I do not agree that it necessarily has any effect at all on blocks that are "too large", depending on who mines them and who they are directly connected to without intermediation of any of the proposed prejudiced nodes.

The top 51% of hash power can pump out blocks as huge as they choose to, everyone else is disenfranchised. You might as well try to stop a 51% attack by ignoring or refusing any block that contains a payment to a known major manufacturer of ASICs so the 51% attacker won't be able to buy enough ASICs to reach 51%. Oops, too late, they already are there. They but lack an opportunity for "spontaneous order" to hook them up into a "conspiracy" that is simply "emergent", not at all pre-meditated - in particular not premeditated-as-in-foreseen* by whoever got rid of the cap on block size, since they would seem to have apparently imagined some completely different "spontaneous order" than that in which whoever has the most [brute, in this case] force wins?

51% attackers can already do plenty of nasty things, now we're gonna hand them carte blanche to spamflood the whole network into oblivion too?

* No, wait, it has been foreseen, so surely if they implement it anyway it is, literally, pre-meditated, isn't it?

-MarkM-