Marv Earl Johnson was an American R&B and soul singer, most notable for performing on the first record to be issued from what became Motown... (wikipedia)
What they are trying to do is make the indecency problem as big an issue as possible.
Down the road when--if there is some sort of finding that there is harm in this--then we're going to see calls to regulate speech because of the potential harm. That's where there's going to be a problem.
It's not a good thing to have somebody like Fred Phelps out there screaming things while your loved one is being buried but unfortunately, he does have a right under the First Amendment to do that.
The use of the word 'annoy' is particularly problematic. What's annoying to one person may not be annoying to someone else.