If people prevent something being used by tons of other people for no good reason, then this would be a very good one to "hold a grudge" against them for.

Are you talking about the DDoSers or the admins of lemmy.world? Because, yes, everyone who is trying to use lemmy.world that can't should hold a grudge against the skids who bought a DDoS service subscription.

If you're talking about the admins, you should be more specific. Are you saying that them defederating from another instance is a good reason for that other instance's users to hold a grudge and DDoS? Because I would bed to differ if that's the case.