Just because guns were used to mass-murder gays (just like guns were used in mass murders of non-gays), doesn't make gun control a gay issue.
Gun control might not be a gay rights issue, but if conservative Republicans stopped enabling hatred, things like this would be less likely to happen. What do they expect people to think or do when they go around calling LGBT people sinful and against God? When you take a bunch of really religious people and fire them up by constantly telling them that some people are sinners and going to hell, it's not a very big leap to think that a few of them might start to get violent. Anyone that knows anything about history will know that a lot of the biggest wars and conflicts in our history were fought over religious people accusing other people of being sinners and against their religion. It's irresponsible, dangerous, and just plain mean.
Before someone responds to me, "but this guy was a muslim!" - Yeah, that's true, but there was another white conservative dude that tried to bring an assault rifle to the LA pride parade on the same day. It's not the religion that matters. It's the hate. That's the thing that those people share in common, and it's the thing that we should be railing against. When there's a bunch of hateful people out there and their political leaders are stoking their passions by villifying vulnerable minority communities, easy access to firearms is just a tangentially related issue that makes it easier for them to take revenge on all of the people they hate.
That's been debunked. And the Orlando shooter was obviously not motivated to commit this shooting by Anti-Gay Republicans, he was motivated by his religion. So no, this shooting wouldn't have been any less likely to happen if Republicans didn't "enable hatred"