I have complex feelings about this church, and the protests in particular. I absolutely believe in free speech. I also believe in exercising my right to free speech, frequently, as good taste and political correctness aren't my forte. I also believe in respecting anyone who chooses to stand up for their country and for their beliefs. The members of the church are obviously standing up for what they believe. They're doing it in a tactless and offensive way, and about offensive and stupid bullshit, but that is pretty much what they're doing.
If the cemetery is on private property, then the patrons/owner do have the right to ask that the protesters leave, and the right to call the police if they don't. Of course, they could cross the street and protest from public grounds.
My general stance, is I have no problem with another person's beliefs until they become a problem for me. Homophobia doesn't bother me personally, unless someone decides to make it a problem for me. I'm gay, some people are super uncomfortable with it, and that's fine. I work with blue-collar guys who were really "concerned" about me being gay at first. By now they realize I'm just a mouthy asshole like they are, I just don't care about the texts of naked chicks they pass around. I believe in the basic principle of "be nice or leave me alone."
I don't think I would want to protest another person's funeral. Obviously this group has decided that their beliefs make room for that kind of activity, but protesting the mourning of another life isn't in line with my beliefs. It would just be- being an asshole for no reason other than I disagreed with their actions. That's not really a value that I hold, it's just a character defect I'm working on.
So, yeah. I think protesting another person's funeral is bullshit. I think it's fucked up and sick behavior, perpetrated by sick, deluded people. Of course, if Americans protested all fucked up and sick behavior, that puts us in very murky moral territory, because who makes the call?