Caligula made his horse Consul. It was the Celtic kings of Britain who had sex with horses (in public, as part of the coronation ceremony).

One point of Boswell's work (both in that book and in "Christianity, Social Tolerance and Homosexuality") is to show that present-day Chritian intolerance of homosexuality is a historical aberration. Most of the history of the Church has a far more creditable record of tolerance than the present era.

Islam can show a similar mixed record, ranging from complete tolerance to complete intolerance. So can animism. One of the few belief systems never to have developed much tolerance to homosexuality anywhere was institutional atheism.