I don't think your comparison to racism works or that anyone has suggested that homophobia is strictly defined as violence. If that were the case then the Westboro Baptist Church wouldn't be considered homophobic which would be ridiculous. It does include hatred / intense dislike though which of course does apply to them.
Words and labels matter do. You can try to label anything as homophobic but if it really isn't, people will question the label and the motive for it. Some people identify so strongly with an issue that they can't see things objectively and want to apply it to the things they blame for their past pains. Credibility is hard to gain but quick and easy to lose when labels are over-applied.
Overreactions don't help a cause, they weaken it. They wear away sympathies because deep down most people want things to be fair whether that is praise or criticism. I'm simply unwilling to take part in the politics of offence on this issue.
While the video isn't pro-gay (duh) that doesn't make it homophobic or promoting discrimination. Sure, people can wave their hands and protest and invent stories of what they think happens after the end of the story but none of that alters the facts of the video itself which is mild, contains no derogatory language and doesn't promote people making judgments or prevention of other people's right to make their own choices.
If that is homophobic, then why is being gay such an issue?