Yes, you would be correct in saying that about period beards. I cover this in my article about Blackbeard that I wrote for my site here, entitled "The Firsts of Blackbeard". Here is the relevant section copied and pasted from my work:

In the same letter that Johnathan Dickinson mentioned the taking of the Betty and other vessels around the Delaware Capes, he also provided the first known reference to Thatch’s famous name, Blackbeard. In one line at the beginning of his letter, Dickinson says the leader of the pirates raiding vessels off Philadelphia was, “One Capan Tatch All[ia]s Bla[ck]beard.”[48] None of the other documents about these early raids mentions this alias. The source of Dickinson’s information is unknown. It would be another seven months before the writing of the next known document to reference the Blackbeard alias.[49] As to why Thatch stood out for having a long beard, the early eighteenth century marked a time when it was unfashionable to wear beards. Shaven faces on men represented enlightenment, propriety, and Europeanism. Beards could represent or symbolize several things to Europeans of the time, including rugged masculinity, uncivility, and discordance with mainstream society.[50] There is no way to know why Thatch grew out his beard, although the choice did help him stand out among his fellow pirates, which could be a potential reason as well. Since Thatch possessed the alias of Blackbeard by the time of his first cruise in the Revenge, it is likely that he began growing the beard long beforehand, though it is impossible to pinpoint the exact time Thatch decided to begin growing his notorious beard.

While Dickinson mentioned Thatch’s alias, the first and only known physical description of Blackbeard by an eyewitness occurred six weeks after Dickinson’s letter. At daybreak on December 5, 1717, ten leagues (about 34 miles) west of Crab Island (also known as the Isla de Vieques, to the southeast of Puerto Rico), Henry Bostock, master of the sloop Margaret, encountered Thatch in his new flagship, the Queen Anne’s Revenge, along with Bonnet’s Revenge. Bostock surrendered to the pirates soon after they fired a warning shot with small arms. Bostock went onboard the Queen Anne’s Revenge and met Thatch, who he described as, “a tall Spare Man with a very black beard which he wore very long.”[51] While Bostock described Thatch as a tall, lean man with a long, dark black beard, Bostock does not mention Thatch’s alias.

This description pales in comparison to Mist’s lengthy, but unverified, description of the famous pirate. Mist described Blackbeard as having a, “large Quantity of Hair, which, like a frightful Meteor, covered his whole Face,…This Beard was black, which he suffered to grow of an extravagant Length; as to Breadth, it came up to his Eyes; he was accustomed to twist it with Ribbons, in small Tails, after the Manner of our Ramilies Wiggs, and turn them about his Ears.”[52] Mist’s text continued with a description of his attire during battle, along with “two or three more of his Extravagancies, which we omitted in the Body of his History.”[53] No other documents corroborate Mist’s claim that Thatch used ribbons in his beard, nor the stories following this description at the end of his chapter on Blackbeard that included some of the more enticing tales within the greater canon of Blackbeard legends. The only other aspect of Mist’s description that matches anything mentioned in any other accounts is the, “Sling over his Shoulders, with three Brace of Pistols, hanging in Holsters like Bandaliers.”[54] During the raid off the Delaware Capes in October of 1717, one report in the Boston News-Letter mentions that, “They have Arms to fire five rounds before they load again.”[55] This brief note refers to the crew in general and to the amount of arms the pirates possessed, since some pirates carried multiple firearms for fire superiority in combat.[56] The report suggests many of the pirates in Thatch’s crew possessed enough muskets and pistols without having to reload immediately to continue firing. Beyond the possession of a long black beard and many firearms, it appears probable that Mist, wishing to entice his audience further, engaged in some factual fiction and decided to augment his work by tacking on his enticing description of Thatch and other stories at the end of Blackbeard’s chapter.

If you want the footnotes, just go to my original article. You might want to check out the article if you plan to do a thesis. By the way, what kind of thesis? A term paper in undergrad, a capstone paper for undergrad, or a master's thesis?

More on beards. I actually included a little work on hair styles of the period in my master's thesis work regarding late seventeenth/early eighteenth century maritime dress for common Anglo-American sailors. Remember, there are no absolutes. Of course you'll find some sailor or pirate with a beard eventually, since some circumstances resulted in it. Maybe that person was lower class and couldn't afford/was tired of trying to shave because of remarkably quick growing facial hair (after all, while this period established a fashion change to beardless - especially because of steel production allowing for cheaper razors - it did still cost money to either buy the razors or to pay someone to shave them). Another possibility, the person was backwards in their thinking and stuck on the fashion of yesteryear in regards to facial hair (especially the perception of masculinity thing). Most likely, you'll see beards in cases where travel/sailing is taking place in more remote areas. Whalers in several period images are depicted with facial hair while engaging in whaling in the cold remote northern waters. But, the social norm was shaven, so more sailors than not would try and shave (or at least keep facial hair down as much as they could, tolerating stubble for a few days wasn't the same as having a beard) when possible, especially when inhabiting a place with other people that weren't sailors. It should also be remember, more sailors than not jumped between land and sea employment. A lot of sailors engaged in many long voyages or ended up stuck in the Navy for several years, but many others went to sea for a few months, then returned home and did another job. A lot of them treated it like seasonal work. The sailor culture of this time wasn't as isolated from general society as some think. It wasn't until the 1690s that the British Navy regularly started keeping sailors for years on end (the tradition beforehand was to do a warm-months campaign and release the sailors back home for winter).