First of all, I'm not entirely sure what you mean by "being gay." I can only assume you mean public displays of affection between two same sex people. I have to agree that there is a level at which public physical affection is a distraction (dare I say offensive) fromanyone, not just gay couples. I'm far more offended by teenager PDA than I am when it is two adults.
To answer your original question, however, I think that today's society (at least in America) is the more accepting of non-traditional relationships than we have ever been in history. In this way, I think that openly gay, or openly bi-racial, or any other non-traditional relationship as portrayed in real life or the media, has helped many teenagers (and others) lose the insecurity that comes from being socially ostracized for one reason or another.
In this way, I have to say that openly gay relationships in our society have had a mostly positive effect on teenagers.