They are both completely different things. One is about two people of the same sex falling in love and wanting a relationship and the other is about getting weird with animals! I'm not even sure how you'd even compare them. Homosexuality is genetic and the other is just plain gross and nasty!
Homosexuality is a perfectly natural desire and expression of love between a two humans of the same sex. Same gender sex is in no way related to interspecies sex. There is ample scientific evidence that suggest homosexuality is caused by processes of brain development. There are many different species of animals that exhibit homosexual behavior, not just humans.
There is no comparison to be had between bestiality and homosexuality. For a human to have relations with an animal is them having sex with the animal with no consent. This is rape. Two consenting people of the same sex is an act of love. These two things are in no way similar.
Two people who are consenting are not even remotely comparable to a person and an unable to consent animal. I don't care how you feel personally about LGBTQ people -- there is no reason to ever, under any circumstances, compare a consenting relationship to one that is essentially animal rape.
I do not believe it is acceptable to make comparisons between homosexuality and bestiality. Homosexuality still deals with sex between two humans, while bestiality refers to a human having sex with animals. The two are not comparable in any real way and they should not be compared. I certainly wouldn't find a persons statements credible if they did compare the two.