People have the right to say what they want (at least in the US, mostly), which includes people voicing their disagreement with stuff. It's a two-way street and we're better off with it that way. You can't force someone to listen to you, just like someone can't force you to listen to them.

What you can do, however, is attempt to educate people if they're willing to be educated. If successful in doing so, you help decrease the amount of bigotry that exists. In my opinion, attempting to engage with an individual to determine their intent is a way of dealing with it. Why stay silent when you could help make the world a better place?