If someone donates money to support a bill to make it illegal for straight people to marry, then the comparison might be justified. Until then, equating a private, in-born sexual preference (or opinions of such) with attempting to enshrine bigotry in the law is really stretching things.

Were people ever arguing that, or were they arguing that people shouldn't be fired because of their sexual preferences? Are racial minorities being fired because of their opinions about race?

Racial minorities being fired because of their opinion about race - ie, their opinion that they should have the same treatments are whites - was very common as far as I know. To make a different example, the new laws in Russia aren't against "being gay", they are against those who argue for the rights of gays.