The reality of Purgatory is a dogmatic pronouncement and anyone, regardless if he is a cardinal, bishop, priest, nun, or catholic lay person who says Purgatory is an invention, not only departs from catholic teaching but is a heretic. A heretic is defined as someone who denies a dogmatic infallible teaching of the church. This priest you mention seems he needs to go back to the seminary, as per the reason he seems to be theologically confused. Yes, speack with him, and if he is humble enough to listen to you on this matter, thank him if he corrects himself. he can beleive whatever he personally desires, (not even he is under a vow of obedience) but to pass him hypothetical invalid oipions on a dogmatic pronouncemet, that he has no right to do, especially if in the public prayer of the Church: the Mass, which is not his, but the Church’s.
You may want to write a letter to both his superior (if he is a religious order priest) and to the Bishop. If these don’t work, please consider writing a letter to cardinal Josef Ratzinger of the Congregation for the Doctrine of the Faith(I am sure he won’t be very happy if that priest keeps teaching there is NO purgatory).
many blessings, and lets continue to pray for young vocations to orthodox seminaries, and that the liberal ones over age 50 may change, and get out of the 1960’s 1970’s mindset.