They have no other arguments any longer.  The only remaining talking point they have is that if we raise the block size limit too much that it will result in centralization (without a clear definition for what this means).  

This is why I'm pushing my new talking point: how can a group enforce a production quota that fights the free market?

My point is that even if they are right (and they aren't) there is still nothing that can be done about it long term.  Bitcoin will break down dams erected by special interest groups attempting to block the river of transactions.