Yep. Grenades in MY past are always duds, otherwise I wouldn’t be here to talk about them. It doesn’t matter if they were fake, or malfunctioned, or had a pseudorandom or quantum probability to blow up. Past throwers of grenades are only relevant in the sense that they are evidence of future grenade-throwing.

I would still kill them, even if I knew they were now completely reformed or impotent. If convenient, I'd beat them to death with a single box just to ram the point home.