In the U.S. of A., picketing funerals is a Constitutional right, according to the Supreme Court. Given that, I just want to make the highly unoriginal point that just being legal is not enough to make something okay.
The irony here is that Westboro Baptist and other picketing fundamentalists (if any even exist outside of crazy Westboro Baptists) would agree with me. They would argue that legalizing same-sex marriage or abortion doesn’t make it right or acceptable in the eyes of God. In fact, they’d argue, it’s so repugnant to God that we’re actually doing the right thing by picketing these funerals, raising people’s awareness of His coming wrath.
And yet, somehow they don’t get the fundamental rule of social courtesy: that you don’t treat somebody in a way you wouldn’t want yourself treated. That there are certain social boundaries that need to be respected, and one could make the argument that customs around saying farewell to a loved one are some of the most important. The message about how much God hates fags/abortion/you can come later.