Vegetarianism as a spiritual practice akin to Eastern religions is heretical as per St Paul in his First Epistle to Timothy (4:3)
"Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils...Forbidding to marry, and commanding to abstain from meats, which God hath created to be received with thanksgiving of them which believe and know the truth. For every creature of God is good, and nothing to be refused, if it be received with thanksgiving"
Vegetarianism for health reasons, for ascetic reasons, or out of outrage at factory farming of animals is ok.
What Eastern religions are saying is that eating meat is somehow bad for you, somehow draws you away from God, somehow makes you unclean, somehow makes you a violent killer (just pick up a copy of the Bhagvad Gita produced by the Hare Krishnas, the illustrated version they pass around, showing a meat eater as a frenzied murderer). That is heretical.
Abstaining from meat because of other concerns, or out of self-restraint that does not involve denying that the practice of eating meat is not intrinsically evil (as monks do) is fine.