It depends on the context. If you’re calling someone gay because they’re actually gay and it’s a relevant situation, or if you’re coming out yourself, or speaking on LGBT+ issues, etc. then no, but if you’re calling someone gay because it’s a *slightly* better insult than a “your mom” joke, then it is an insult. In other words, it’s not supposed to be an insult, but some people have taken it to be.