The proportion of the population of debian-legal who believe that the patch clause exemption in DFSG 4 is a grave mistake or that the GPL is only free because of DFSG 10 seems greater than in the developer population at large. That seems like a reasonable approximation of "extreme".
I see how you could measure this appearance: for example, by using the number of unique posters/developers making such statements compared to the total number of posters/developers; but I'm not sure of the technicalities of doing it. Can you post the methodology and results you used, please? It will be very useful for some other situations.
-- MJR/slef My Opinion Only and not of any group I know http://www.ttllp.co.uk/ for creative copyleft computing