I certainly can appreciate the civil libertarian point of view on this. I concur that we need to be mighty careful with setting any precedent involving the abridgment of free speech. But...
(Warning: semi-rant ahead, not directed at anyone here)
I do see a tendency amongst some on the Left to value the rights of people in direct proportion to how deviant, crazy, psychotic or otherwise contrary to societal norms they are. Too much of a tendency to identify people like that as part of some oppressed group and want to accord them special treatment and bend over backwards to cater to them.
While I'm in favor of reasonable protections for unpopular or even bizarre viewpoints, ordinary, tax-paying normal everyday working people conducting a funeral for a loved one who gave his or her life defending our country--well, guess what, THEY have rights, too. I'm seeing too much focus on the right of people to act like moron sociopaths, and not enough on the rights of people to peaceably conduct funerary rites like normal society has done for millennia. Presumably because a common Christian funeral is, well, not bizarre enough to merit protection.
I think a precedent should be set: normal people have rights, too. When a funeral is being conducted, the people conducting it have the floor. Asshats with sociopath slogans and bullhorns, can, to put it bluntly, drink a nice big cup of STFU while the funeral is in progress. They can protest before the funeral. They can protest after the funeral. In locations and times where funerals are not being conducted, they can shout whatever hateful, pea-brained slogans pop into their 8-bit brains. But at the funeral...the rights of NORMAL people hold sway.