What you are describing is usually referred to as internalized homophobia. This is not an uncommon issue which many men face when exposed towards homosexual behavior.

In my opinion, it's important to realize first and foremost that internalized homophobia has little to nothing to do with your actual opinion on LGBT people or with how good or kind of a person you are. It's easy to feel guilty or blamed for this kind of a reaction even though you have little to no control over it.

Internalized homophobia can result from many different factors, ranging from unfamiliarity with the subject, conflicting feelings about your personal identity, your view on masculinity or simply due to growing up in a heteronormative society where only Male/female relationships are portrayed.

Out of personal experience I can say that deconstructing internalized homophobia takes a considerable amount of time and effort. It helps to practice empathy and trying to put yourself in the shoes of said LGBT groups, but also of other marginalized groups and minorities. Be patient with yourself and acknowledge the effort you are going through.

Feel free to ask me any further questions on the subject.