Is Luke-Jr the only person thinking what he thinks or are others BTC core dev agree with him?
I think the reason people in this thread are so wound up is because there is a perception (from Jgarzik's comments in part, but of course from the OP_Return from 80 to 40 change as a whole), that Luke Jr's opinion/attitude is very much indicative of the position of the the other core developers as well. (Especially since none of them have come forward to provide sound technical reasoning for the change).
OK.
What would happen if there is a consensus in the BTC community that one guy shouldn't be a core developper anymore. Does a procedure exist?
If there isn't such a procedure there ought to be. It's pretty clear from Luke's entire posting history that he is a constant source of friction, and takes obvious delight in it.
I'm inclining to agree with Adam that the biggest problem with bitcoin is the core devs, and that the best course of action for Counterparty is to expect nothing from them, except perhaps deliberate obstructiveness, and move to considering Litecoin, or some other faster blockchain without the baggage of these guys. I don't see much constructive development from them over the last year in comparison to what the Counterparty devs have acheived in a few weeks anyway. They seem a lot more like traffic cops than devs on any open source project I've come across.
The bottom line is that without innovation Bitcoin is going to be left behind. It's a shame to throw away all that hashing power and first mover advantage, but from the silence of any of the other 'Big 15', and the attitude of Luke and Jeff in this thread it seems pointess to keep begging for a tiny peice of their territory to work with because they have made it very clear that they just don't care about what Counterparty is attempting.