Edit: in light of the discussion, I think the solution would be to remove all airdropped merit as NeuroticFish suggests.
Personally, I wouldn't mind if someone took 1000 merits from me, I didn't ask for them or invent the merit system, and I had already reached Legendary rank before the system came to life. However, I do not think that we should go to such drastic measures to punish some individual cases that behave like leeches on the forum, but that airdropped merits could be taken away from those who really proved to be members who have no contribution to the forum.
Yet if you consider that the issue of removing airdropped merits has been the subject of debate many times, and that there has been no concrete response from the admin (as far as I personally remember) - I think such a move is very unlikely.
It was a reward for loyalty, and you want it taken away?
Don’t confuse loyalty with the fact that before the merit system, every (literally) spammer and shitppster could get hold of any rank without writing at least one quality and meaningful post. The member listed in the OP is a classic example of someone who would never become a Full Member in today’s system, so we can’t say that his airdropped merits are a reward for loyalty.
It wouldn't solve anything, and I'm not sure how many of you would be active if the merits and signature campaign is taken away from the forum.
Most of the new members who started from scratch are not in any danger of being deprived of something, and most of the active members have collected several times more merits over the years than they received based on the rank they had when the merits system was introduced.