Maybe, but ask yourself why you need to tell someone. What are you getting out of it by telling someone when they are acting like a selfish jerk? Does it change their behavior? If not, then why bother?
It really depends on the topic. The Bible does say that we can judge in righteousness so then that becomes what is the definition of righteousness. That depends on the individual. If they are Christian, then use the Bible to point out the error, if they follow a different path, maybe study what the person uses as their "Religion". To use "your" beliefs on someone with different beliefs...not so good.
I judge the church for lying and call them liers. I judge anti-gay people for hating out of fear and ignorance and call them homophobes. I judge mysoginists for treating women like they're less than or racists for being ugly to people based on their genetics.
But, I also try to realize that each person has a background that built them and take that into consideration.
I have also lived a very kharmic life, sometimes that felt a bit painful but it has also educated me and made me less ignorant to the plight of others.
So these days I ask myself if I'm willing to get a kharmic slapdown if I judge a person/entity. If I truly feel I can stand by that judgement then I make it.
If you are uncomfortable labelling them (and afraid they'll turn it on you), just tell them their behavior is unacceptable. Tell them that you don't accept their opinion of you. Or that what they think of you is none of their business. Or that judgement based on false "standards" is faulty.
In other words, just set boundaries.
And it's not self-righteous or judgemental to recognize what's actually there. In my mind, self-righteousness, is when a person tries to make themselves feel better about themselves by showing off their superiority or putting others down. Recognizing when somebody does that is just normal.
Somebody posted a comment about an interview with "octomom" Nadya Suleman and a bunch of people chimed in about how she was making a living (porn) was so wrong and she should have her kids taken away and on and on. When I commented that she had done nothing illegal, at least not illegal where she lives, and therefore had done nothing to justify having her kids removed I was attacked for causing problems. People truly amaze me sometimes.
Note: My defense of octomom's career choice is in no way an enforcement.