w/e like what you like as long as you aren't intrusive with it. once it becomes obnoxious it becomes an issue, not because you like it, but because you're being obnoxious.
as far as i'm concerned, being a brony is indicative of an interest in a show. not of some severe psychological complex; this varies from person-to-person, even if some bollocks psychological complex might cause you to be more likely to become a brony.