If a man is involved in a sin of any type, can he ask other people to don't do that sin, in other words can a bad man stop others from the same sin?
A person engaged in a sin or even if he is following a way that is not the best way, should not correct other to abstain from that sin or to follow a better path. This is because he then is not practicing what he himself preaches. This is mentioned in the Quran in chapter Baqarah. It is disliked by God.
Enjoin ye righteousness upon mankind while ye yourselves forget (to practise it)? And ye are readers of the Scripture! Have ye then no sense? (2:44).
I think this is a good practice to stop other person to do bad. may be when other person do some good work and stay away from sins due to advice of bad person there is nothing wrong. bad person is bad but this is the matter of that person. Give advice to other person is I think not wrong.