From the Mafia, I cannot tell you exactly. I can, however, give you some insight into how much a man with the same demographic characteristics as Tony Soprano might have viewed active (rather than receptive) oral sex. [Edit: I have learned that the character who said this is not Tony but rather a much old character. See my note below.]

The first thing I want to emphasize is that the sexual habits of people in the West changed wildly during the 1960's. One of the most fascinating books I've ever encountered is Sex Before the Sexual Revolution. It's an oral history of England, rather than America, but it suggests that even romantic kissing with tongue ("french kissing") was rare in this period. I believe in all the people they conducted the oral history with, only Of course, as some of my favorite answers from /u/mimicofmodes "What was courtship like before dating became a 'thing'?” and "How common were 'Flappers' during the roaring 20s?" show, sex and dating had been changing wildly for many decades before that. Which is just to say, as the show implies, this norms were in flux. You might be interested in my older answer "Is it true that oral sex was rarely performed by prostitutes in the USA before WWII? If so, why?" As I say in that post, I think the contemporary survey evidence shows that oral sex (performed by either sex) only seems to become widespread in American in the 70's and 80's. (The study I discuss below argues it happened slightly earlier, in the late 1960's, but I am not convinced of it.)

Despite the fact it appears not to have been common in America before the 60's-80's, the idea that men giving oral sex was seen as unmasculine is quite old. As many historians, anthropologists, and sociologists have pointed out, in many cultures (from ancient Rome to contemporary American prisons), the dividing line isn't always between men who have sex with women ("straight men") and men who have sex with men ("gay men"), but rather the penetrator and the penetrated. This applies not just anal and vaginal sex, but also oral sex. Indeed, in Ancient Rome, there is sense a receiving oral sex was penetrative and giving oral sex was being penetrated, and therefore unfit for a "real man". See this very old answer from /u/heyheymse or this one /u/Whoosier. While I wouldn't draw a direct lineage between Roman sex norms and mid-century American ones, I think there is likely something analogous going on, in that there is more to proper sexual functioning in the character's worldview than merely "heterosexual" and "homosexual". "Penetrator" and "penetrated" is, of course, one ancient alternative, though as the above answers say, these classifications tend to be more implied and deducible from patterns rather than explicitly stated, so I'm not sure Tony would consciously realize that he was mapping those two general categories onto his perceptions of various sex acts.

Now, as for how prevalent active and receptive oral sex was for men of Tony Soprano's age and social class, we can actually answer that fairly well. Representative surveys of sex behavior only really became possible with the AIDS crisis (before that, you had to rely on things like the Kinsey Reports which use non-random, non-representative samples—and before Kinsey, we don't even have that). And once Congress realized that public money was being used to fund a survey on sex that wasn't closely targeted on merely public health but rather on understanding sexual behavior more generally, they pulled the funding plug, so there is really only one representative sample of America that looks at sexual behavior broadly: the 1994 study led by Edward Laumann that was published as the Social Organization of Sexuality (academic) and Sex in America (popular press). There is at least one academic nationally representative-sample survey of sexual behavior in America funded by a condom company after this and a few of other subsequent studies of other Western countries, but this is very close to a unique study.

Looking at the chart on page 98 of The Social Organization of Sexuality, we see that the overall lifetime prevalence of active oral sex for American men was 76.6% and the overall prevalence of receptive oral sex was only slightly higher, 78.7%. For married men, it was even higher (active 79.9%; receptive 80.4%). However, those numbers are for whether the respondent had ever given or received oral sex—the numbers for men who'd given or received oral sex in their last sexual encounter are much lower—26.8% and 27.5%, respectively For White men, rates of both lifetime and last encounter, active and receptive oral sex are considerably higher than for those of men of other races (for example, White lifetime active: 81.4%, comparable rates for Black, Hispanic, and Asian men are 50.5%, 70.7%, and 63.6%, respectively). Catholics—Tony's religious group—are the most likely group of men to have ever given oral sex, though the religiously non-affiliated are slightly more likely to have ever received oral sex or to have given or received oral sex in their last encounter. Based on multiple regression analysis, the authors argue that religion it self has little independent effect—unlike race—and most of the differences in religion are driven by the fact that different religious groups have different levels of education. I'm not a big fan of the show, but I believe Tony has some college education but even if he's just a high school graduate, all groups besides "less than high school" have lifetime rates above 75% (less than high school: 59.2%) and all groups that have at least some college are lifetime over 80%, though his peers likely have less education, perhaps one of the reason for this social strain. For men born 1958-1962 (Wikipedia tells me Tony was born in 1959), more than 75% reported lifetime both active and receptive oral sex and roughly 83% reported lifetime either active or receptive oral sex. As they say, "roughly 8% of men and women have experienced one type of oral sex", and of those, most only had engaged in receptive oral sex. So by early 90's, most sexual active Americans had engaged in oral sex, oral sex is nevertheless only a part of a minority of sexual encounters, and, though the data don't spell this out explicitly, the story they seem to tell is that most oral sex is reciprocated.

What do we get from this? Well, let's compare oral sex to vaginal sex and anal sex. In the sample, 95% of men and 97% of women reported lifetime occurrence of vaginal sex ("with only marginally fewer reporting its occurrence in their last sexual event"). Meanwhile, only 25.6% of men and 20.4% of women reported lifetime occurrence of anal sex and 2.3% and 1.2%, respectively, reporting it during their last sexual encounter (9.6% and 8.6% reported having anal sex in the prior year, however—unfortunately, the study does not report equivalent figures for oral sex). One thing that we can gather from this is that the vast majority of men in Tony's socio-economic class broadly had given and received oral sex before, but it's worth noting that this doesn't necessarily mean that they engaged in either form frequently. In general, the data seems to suggest (but not conclusively prove) that most oral sex is reciprocated.

One interesting thing they point out is that though "beginning in the 1920's, the sexual script for opposite gender sex has become increasingly elaborate to d to include more kissing, more caressing of the body, more manual genital contact and, more recently, more oral sex", nonetheless "the ultimate goal has largely remained vaginal intercourse." And while oral sex has become much more common over time—notably increasing with those who were born in the mid-to-late 40's and therefore came of age in the late 60's—there does appear to be a "lingering normative constraint on [the] sexual practices" of older people and more working class groups, particularly in regards to oral sex.

One thing to note, however, is that this is what people are telling surveyors. For some questions (like total number of partners), there is a clear mismatch between the answers of men and women, but for oral sex, the numbers tend to be relatively close, which to me makes me think they are likely to be fairly accurate. While I was in graduate school, one project I was working on but never finished was an argument about sexual taste and knowledge. The main point (based on my own analysis of Laummann's raw data, as well as similar studies) is that there doesn't appear to great diffusion of information about what people are actually doing and liking in terms of sex. Tony may think that none of his friends engage in active oral sex, but that doesn't necessarily mean that they haven't. Indeed, the survey data seems to indicate that most of them likely have engaged in oral active sex, though the data is much less indicative about how frequently they might engage in active (or receptive) oral sex. It does not, however, seem to be necessarily an "isolated experimental incident associated with multiple partners", as the study characterizes anal sex. Certainly, men like Tony would engage in oral sex much less often than they engage in vaginal sex, but also likely more often than they engage in other partnered sexual activity beyond kissing and groping.

(see also my note below)

oral sex has become much more common over time

Could part of this trend be attributed to better hygiene habits? Your answer touches on psychological aspects of “masculine/feminine” and “penetrating/penetrated”, but what about better overall hygiene habits, access to running water, less restrictive clothing (which may reduce build up of sweat and odors, etc.)?

Also, your answer is exclusively about heterosexual sex. Do the same numbers - implying aversion to oral sex that only gradually decreased over generations - hold true for lesbian and gay sex?