I think it's entirely reasonable for people to disagree on the proper way to commemorate a complex tragedy like that of Jovan Belcher, who killed his girlfriend before killing himself. Of those who argued for the Chiefs game going on as scheduled because football provides a distraction from the awful parts of life, and those who said the game should have been postponed because it was unfair to ask Chiefs players and coaches to take the field so soon after a traumatizing event, neither side was "wrong"—they were just stating their opinions.
You can see both sides of the argument on how Belcher should have been commemorated. It's easy to grasp the argument that Belcher was a murderer before he was a suicide, that taking his own life is the only thing that separates him from Rae Carruth or O.J. Simpson and he shouldn't be celebrated for it, that it's an insult to Kasandra Perkins's death to marginalize her for her more famous killer. On the other hand, Belcher was the famous one, and the only reason fans feel a connection to this horror at all. He was clearly a very troubled person, and if he wasn't strictly a tragic figure, it's impossible to expect those who knew him in life to vilify him now.
It's definitely OK to turn this into a public debate on larger issues. If the wake of nationally relevant firearm deaths isn't the time to bring up gun control, when is? But this runs the risk of polarizing a tragedy for political means, and distracting from the perhaps more germane issue of mental illness.
Everyone deals with sadness in their own way, and there's no single "right" way to mourn, especially when tragedy and crime intermix. Maybe the only "wrong" thing you can do is tell someone else that their grief isn't the right kind of grief, as if that's something that can be dictated. Any way someone chooses to react to Jovan Belcher's murder-suicide—yes, even with dark humor—is fine if it works for them.
That said, spelling "Javon" Belcher's name wrong on the commemorative t-shirt is definitely the wrong way to grieve.