For my part, this IS an issue, especially at a time when so many kids are subject to such homophobic malice that they are succumbing to despair and committing suicide. In part for the reasons laid out by David Pakman. This was an illegal act, it was malicious, and it was handled badly in the media by Mitt Romney in such a way that Romney was obviously lying about some part of this story. This was not merely some stupid prank, this was a kid who was targeted and assaulted.
Something that was not said in the video is the fact that when an anti-bullying task force was formed in Massachusetts while Romney was governor, Romney eventually snuffed the task force out. Obviously his animus towards the LGBT community has not abated, he is just slightly better at hiding it by not openly/physically attacking gay people. His views are still there, and he clearly has never seen LGBT people as equals under the law, and he still doesn't. That, so far as I'm concerned, is reason enough for me to not vote for him.