No we cant "condemn" sinners, if in the sense of "condemn" we mean consign to Hell, for that as has been pointed out before is Gods prerogative alone, and he alone has ALL the information to come to a perfect judgement, we on the other hand, are wretched sinners ourselves, our faith and so called morality twisted and perverted by our sinfulness, unable to judge our own salvation let alone the salvation or otherwise of others. But we can judge the sin, by following christs teachings and commandments we can see how we deviate so much from what he asks of us and must hope and pray that God indeed, is very, very merciful and forgiving, for we are ALL in dire need of his Grace.
One thing that always gets to me when the subject of "sin" and "condemnation" arises in discussion is how quick some Christians are to point the finger at Sexual immorality, particularly the sins of the LBBTQ community, or as someone referred to them lovingly as, "the Alphabet people", i must remember that phrase, a definite example of Christs love and compassion as well as our own wretched sinfulness., while ignoring the biggest condemnation Christ had, which was for the rich, the hypocrites and those that ignored the sufferings of the poor and oppressed, and to the best of my knowledge he never once even mentioned Homosexuality. Which isnt to say its not a sin, but that it would seem to come well down Christs list of "degrees of sin".
Could it just be that those sins, those of greed and indifference to the sufferings of the poor, are the very sins that we, in the rich world, are most guilty of, and its always far easier to try to deflect our own guilt by pointing out the sins of others.