Lol, that is by no chance a pre-requisite. I lost count for beef/pork eating supposedly high caste members in the West, who at the same time were shaved head, janeu/tilaka wearing, and demonstratively religious.
Now tilaka etc. Slightly more likely but bear in mind (I presume you are North Indian based on your spelling of janoi am I right?) in many places vegetarianism isn't an absolute norm even amongst Brahmans. Also I would presume purely as a matter of sociology vegetarianism would be one of the distinctive features least likely to go because it is something increasingly fashionable in the larger community whereas janoi etc. are not.
You should just discriminate based on something straightforward like car size or hat color