I don't think the Opebophiles are dumb enough to equate 9/11 and Opebo. They didn't take themselves so seriously.
Still, it's the sentiment. The avatar removal is a show of respect by the individual. It's not someone else's place to decide if an action is "respectful enough" or not.
Who is arguing that it's not "respectful enough"? I think the complaint is that it's lame and empty.
Also, pretty sure tons of people thought the "opebo solidarity" stuff was ridiculous besides the few obsessed fans he has...