I can speak a bit about the Parthians. In essence, it was a mixed bag, because in some cases, there was respect, in others not so much. Here is a quote from Justin epitomizing Trogus:

"Each man has several wives, for the sake of gratifying desire with different objects. They punish no clime more severely than adultery, and accordingly they not only exclude their women from entertainments, but forbid them the very sight of men. They eat no flesh but that which they take in hunting. They ride on horseback on all occasions; on horses they go to war, and to feasts; on horses they discharge public and private duties; on horses they go abroad, meet together, traffic, and converse. Indeed the difference between slaves and freemen is, that slaves go on foot, but freemen only on horseback. Their general mode of sepulture is dilaniation by birds or dogs, the bare bones they at last bury in the ground.[6] In their superstitions and worship of the gods, the principal veneration is paid to rivers, The disposition of the people is proud, quarrelsome, faithless, and insolent; for a certain roughness of behaviour they think becoming to men, and gentleness only to women. They are always restless, and ready for any commotion, at home or abroad; taciturn by nature; more ready to act than speak, and consequently shrouding both their successes and miscarriages in silence. They obey their princes, not from humility, but from fear. They are libidinous, but frugal in diet. To their word or promise they have no regard, except as far as suits their interest." --Justin 41.3

As you can see, some of these ideas seem a little ridiculous: only eating meat that has been hunted? Or doing everything on horseback? And here is the thing, I can't prove to you that Justin was right or wrong, and as much as I want to believe that he is wrong, as before I can't prove it. However, what I can say is that we should look at the sources critically, and realize that owing to the geopolitical hostility between Rome and Parthia, it makes sense that Trogus would stereotype. And since stereotypes have some basis in fact, we can argue that a few elements from the account have some basis in truth. I also am not sure where the supposed homo-erotic attitudes towards the Parthians are expressed, I have not heard of it in the sources. If you could provide that, I would be very thankful.

Ok, now that I think I have answered your question, I am going to hijack it to make a point: sometimes modern historians (particularly, military historians) look down on the Parthians. They are viewed as weak, and not really a challenge to the Romans and had Trajan only been younger, the Romans would have pushed into India. I hate this idea--I really do--because it sort of washes away the accomplishments and capability of the Parthians. This was a power that was an minor, unimportant border kingdom in the 240s BC, and arose to prominence in the 170s BC to go toe-to-toe with arguably the most powerful empire at the time (the Seleukids) and basically reduce them to Syria and its environs. Or how about the fact that the Romans had been running a train through the Mediterranean in the Second and First centuries BC, conquering powers left and right, and yet outside Carrhae, with a mere army of 10,000 men against 40,000 Romans, Surena defeated them in battle. But no guys, that was a fluke, because Crassus was basically an idiot, and had a true Roman general been there like Caesar and Pompey, the Parthians would have been wrecked. You see that happens? The battle becomes a Roman defeat, not a Parthian victory. And I bring all these points (not directed at you OP, you have been quite respectful and naturally critical of Roman-centricness--a good quality in an ancient historian) because too often in my experiences, people will belittle the Parthians in contrast to the Romans and we can see it a bit in some popular historians--most particularity Dan Carlin (he did an AMA a few years ago here, and basically dismissed the Parthians and their army). In fact, I would rather trust ancient authors about their perceptions of the Parthians--

Justin again: "Being assailed by the Romans, also, in three wars, under the conduct of the greatest generals, and at the most flourishing period of the republic, they alone, of all nations, were not only a match for them, but came off victorious; though it may have been a greater glory to them, indeed, to have been able to rise amidst the Assyrian, Median, and Persian empires, so celebrated of o]d, and the most powerful dominion of Bactria, peopled with a thousand cities, than to have been victorious in war against a people that came from a distance; especially when they were continually harassed by severe wars with the Scythians and other neighboring nations, and pressed with various other formidable contests."

You can see not only that the Parthians defeated the Romans, but also had to contend with neighboring powers and yet despite the terrible geopolitical situation, they fell finally to an internal revolt.

Hello there! Many thanks to /u/XenophonTheAthenian for summoning me here; since s/he (?) and /u/tobymoby616 have already made excellent remarks about the nature and value of ancient historiography, I won't comment further on that issue. I can answer your question about Carthaginian child sacrifice, however.

First and foremost, archaeologists have uncovered tens of thousands of urns containing the cremated remains of infants at Carthage and other Phoenician-Punic sites throughout the Western Mediterranean. The most recent analyses confirm that the majority of the victims died between the ages of one and one-and-a-half months, whereas infant deaths by natural causes typically occur within the first week after birth.

Second, Punic votive inscriptions often mention mlk b‘l, "the sacrifice/offering of a citizen/person," or mlk ‘dm, "the sacrifice/offering of a human being"; these are distinguished from mlk ‘mr, "the sacrifice/offering of a lamb/sheep." The texts sometimes add the phrase bš(‘)rm b(n)tm, which apparently means "as his own flesh," thus underscoring the very personal nature of the sacrifice. The victims were offered to Baal Hammon together with his consort Tanit.

Third, as you already observed, the rite of child sacrifice is mentioned not only in the Hebrew Bible (and there's nothing wrong with using it as a historical source!) but also in Greco-Roman literature. The notion that these references all reflect "propaganda" is rather unconvincing. In the case of the classical sources, you'll find that the few authors who comment on the practice (i.e., Clitarchus, Ennius, Diodorus, Plutarch) do not specifically condemn the Carthaginians despite treating it as an oddity. The Romans themselves, moreover, occasionally made human (though not child) sacrifices in times of crisis.

In sum, the archaeological, epigraphic, and literary evidence all indicate that the Carthaginians performed ritual infanticide. As abhorrent as we may find it to be, remember that many Carthaginians must have considered it an important aspect of their religion and identity.

I hope you find this helpful. Please let me know if you have any questions! :)

Select sources and further reading: Patricia Smith et al., "Aging cremated infants: the problem of sacrifice at the Tophet of Carthage," Antiquity 85 (2011): 859-74; idem., "Age estimations attest to infant sacrifice at the Carthage Tophet," Antiquity 87 (2013): 1191-9; Paolo Xella et al., "Phoenician bones of contention," Antiquity 87 (2013): 1199-207; Maria Giulia Amadasi Guzzo and José Ángel Zamora López, "The Epigraphy of the Tophet," Studi Epigrafici e Linguistici sul Vicino Oriente Antico 30 (2013): 159-92.