Gun violence doesn’t just happen to other people, it happens randomly and to anyone, even those who choose not to own guns.
Pointing out the irony that he died because of gun violence despite stating that gun violence is an acceptable cost is mean spirited and insensitive in the moment, but not incorrect.
He advocated for circumstances for which this could happen, he probably just assumed it would never happen to him.
This is no different than many of us who think that the 1st amendment is worth retaining even if people use it to hire hitman or coordinate kidnappings and what not.
Plenty of people use free speech to do bad things. Look at Trump using his rhetoric to get into power. Or outside the US you can see all sorts of crazy leaders gaining power.