Nothing happens in a vacuum. The 1991 riots didn't happen because "lulz, let's kill whitey". They happened because of the total failure of justice where white cops, beat a black man half to death, and were acquitted by an all-white jury. It was essentially 90's Trayvon Martin - and had there been rioting after Zimmerman's acquittal, I wouldn't have cheered them on, but I wouldn't have laid the blame squarely at black people's feet.
If their were riots after the Zimmerman verdict (something I feared, living in a fairly black area and understanding their anger), the blame none the less would be on the hands of the individual troublemakers who would have created the unrest. Thank God that the Martin parents urged restraint in the face of their injustice, because I fully expected riots in Sanford (and if those riots were not handled well by police, riots all the way down here!)
Injustice in response to injustice is and always will be injustice, and their is no excuse for lawlessness even when the law is not followed.