impugn (to attack as false or questionable; challenge in argument)
pugnacious (combative in nature; belligerent)
repugnant (arousing disgust or aversion; offensive or repulsive)
Definitions are taken from:
The American Heritage® Dictionary of the English Language, Third Edition copyright © 1992 by Houghton Mifflin Company.
Electronic version licensed from InfoSoft International, Inc. All rights reserved.
Webster's Third New International Dictionary, Unabridged. Merriam-Webster, 2002.
https://unabridged.merriam-webster.com (30 Sep. 2006).
English-Word Information: Word Info about English Vocabulary (wordinfo.info).