I have a suggestion. Instead of making assumptions and jumping to conclusions about why they are there, I suggest to actually go over to these boys and speak in a nonjudgemental way and inquire why they are there or what they are doing. This doesn’t have to be direct, but done with sincerity. When you feel that there is something wrong, only then would I recommend contacting the right people to intercede on their behalf. All this back and forth talk is wasted time. Get up and see if it’s harmful or harmless, but be sure you are doing it for the right reasons not for your own curiosity or self rightiousness (sp?). Please remember that there are many bachurim out there that may have problems at home or may have difficulty with all the pressures that yeshivos may put on some bachurim that cannot keep up with the pace of things. Some rachmanus helps and trying to be dan lkaf zchus or understanding of each individual. Such blanket statements that “bachurim should never be in a bar” is quite naive in our day and age. Unfortunately, there are many bachurim nowadays that are troubled adn may not be dealt with proper guidance.
So, lgbg, next time you see such a thing, inform us of what you did to try to understand the situation.