Please have a one word answer; and it is not zealot. Zealots are idealists. Being a racist has a very negative connotation. Also maintain the same part of speech. I would like a noun.
The word 'sectarian' is, of religion, closest to parallel with 'racist':
3. A bigoted adherent of a sect; one whose views or sympathies are sectarian.
["sectarian, adj. and n.". OED Online. September 2015. Oxford University Press. http://www.oed.com/view/Entry/174583?redirectedFrom=sectarian (accessed December 08, 2015).]
'Sectarianist' is also in use. Examples include
(From Dialogue and Universalism, Volume 6, Issues 7-12, Warsaw University, Centre of Universalism, 1996.) And
Nobody who can see and write so brilliantly and fearlessly about the evils of religion as he had done would take back what he said just like that. How can a highly spiritual person like him suddenly reduce himself to a mere sectarianist?
(From Transcending Rizal, Margarita Ventenilla Hamada, Giraffe Books, 2005.)
'Sectarianist', however, has not established itself in dictionaries, although the intended meaning is clear.
You can use 'bigot';
a person who strongly and unfairly dislikes other people, ideas, etc. A person who hates or refuses to accept the members of a particular group (such as a racial or religious group).