How many letters does the top answer for “discriminatory especially on the basis of race or religion” have?

The most common answer is antiblack (9 letters).

Crossword clue: discriminatory especially on the basis of race or religion

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

antiblack 9 letters wn-def

discriminatory especially on the basis of race or religion

racist 6 letters wn-def

a person with a prejudiced belief that one racial group is superior to others