Attacking an opponent's character made him no different (2,7)
I believe the answer is:
ad hominem
'attacking an opponent's character' is the definition.
I can't judge whether this defines the answer.
'made him no different' is the wordplay.
'different' indicates an anagram.
'made'+'him'+'no'='madehimno'
'madehimno' with letters rearranged gives 'AD HOMINEM'.
Can you help me to learn more?
(Other definitions for ad hominem that I've seen before include "to man personally" , "Relating to particular individual" , "Latin phrase for argument that attacks opponent rather than debates the issue" , "Directed at particular person" , "(Of an argument) personal rather than objective (Latin)" .)