It comes to mind that there are actually two problems with that.
First is the obvious one - he was arrested for carrying a knife that was not illegal to carry.
Second, even if he had been carrying a switchblade, it seems to me that the law against switchblades is plainly a violation of the Second Amendment. Firearms obviously command most of the attention in Second Amendment debates, but knives are clearly "arms" as well. Odd to see so many Freepers cheering for the police arresting someone for carrying a knife....
If the Baltimore Police had arrested a card-carrying NRA Life Member for carrying the exact same knife and the exact same thing had happened to the NRA member that happened to Gray then these same FReepers would be singing a completely different tune.