To argue like this is a crime against humanity (7)
I believe the answer is:
outrage
'a crime against humanity' is the definition.
(thesaurus)
'to argue like this' is the wordplay.
'to argue' can be anagrammed to 'OUTRAGE'.
Though, I'm not sure how this is indicated.
'is' is the link.
Can you help me to learn more?
(Other definitions for outrage that I've seen before include "Act that shocks public opinion, generates anger" , "Appalled reaction" , "furious reaction" , "Extreme indignation" , "Scandal" .)