@Myorn Well, it was mostly about keeping the lineage possible, which is why French and British princes have so often married the widows of their older brothers. It was believed that a husband's brother or wife's sister is practically the same thing. Although it is quite funny to compare this with the general laws about incest of those times, for example, in ancient times my people considered parent x child to be incest if you had sex with your wife in the parent's bed.
When it comes to premarital sex, while it was not considered "as scary" as gay sex, it had similar problems in the eyes of the then moral guardians. Firstly, this deprived young people of the motivation to start a family (of course, Rui is a dubious example, but according to Hagure you can perfectly see the commoner's perception of romantic relationships as sex with a stable partner and nothing more), and secondly, no one needed dubious bastards and venereal diseases.
If the nobles, as in the case of Philip of Orleans, could produce offspring, their gay adventures were of little interest to people. First of all, because sex in the eyes of people of the past was primarily a tool for creating a family and producing children. LGBTQ activists can talk for a long time about tolerance and intellectual enlightenment, but if you pay attention, you will notice that especially tolerance to gay folks began to grow just when the institution of marriage and traditional values began to devalue in society, and therefore people became less takes care of the absence of children or spouses, and as a result, of those who, for obvious reasons, cannot have all this in principle.
