Because of that article about extremes of bigotry ... (7)
I believe the answer is:
thereby
'because of that' is the definition.
(I've seen this before)
'article about extremes of bigotry' is the wordplay.
'article' becomes 'the' (the 'definite article' part of speech).
'about' becomes 're' (regarding**).
'extremes of' means to remove the middle letters.
'bigotry' with its middle removed is 'by'.
'the'+'re'+'by'='THEREBY'
(Other definitions for thereby that I've seen before include "In consequence" , "about that amount" , "For that reason" , "By that means" , "As a result of that" .)