good thing the social sciences aren’t particularly easy to manipulate for propaganda purposes. Yes, sarcasm.
Nothing better than a totally unnatural and immoral upbringing I guess.
"Intervew" means self-reported. There's a huge and acknowledged reporting-bias when people are recounting their own behavior, especially behavior as emotionally fraught as sex and family life.
Naturally, the same deficiencies in methodology would plague any researcher --- pro-homosexual, pro-normal, or strictly unbiased --- because of the nature of the subject. You can't access people's private records against their will; there are no uniform mandatory reporting requirements for medical history; juvenile arrest and conviction records are often destroyed.
But these are questions one must ask.