Companies _already_ implicitly do stuff like this when they donate to e.g. the Salvation Army, an org which itself has an anti-gay agenda. It's "OK" in that it is legal and it is probably not unethical.

Is it be morally right? That depends, but public opinion in the US and in many (but obvs not all) other industrialized nations suggests that it is wrong.

Shareholders can and should vote with their feet if a company takes a position they don't like. Ostensibly that's one of the levers available to you in our glorious free market economy, amirite?

You might alienate religious people, but when I consider the merits of this particular topic, screw 'em. There's no reason their views (a choice) should trump other people's basic human rights.