I can see why you'd think that, and I'm also not one for knee-jerk reactions. I've moderated communities in the past where the rules insisted that heavy discussions and politics were to be taken elsewhere.
However, I think it's quite telling seeing how other instances have blocked them already, and, if you put exploding-heads into the search bar, there's quite a number of anecdotes of the damage they're causing. It's only a matter of time before they get here, and the damage may be subtle and insidious at first. :/
I'll put my opinions aside. Out of curiosity, what makes you think blocking is such an "absolute last resort" that it seems like too drastic an action? I don't really understand what value exploding-heads brings to us, and if it's truly, somehow, the wrong move (personally doubtful), we can always re-federate. I think prioritizing the comfort and safety of users who actually use mander.xyz is more important, since they're the ones contributing content to the instance.
Refreshing doesn't help for me, BTW. Still see the same issue on my end.