How to deal with a male friend in his 70's who denies kissing and fondling women.

This is outside the realm of caregiving, but does concern inappropriate behavior by a senior person. This man has been active in several 12-step meetings for decades; the kissing began a couple of years ago and has now progressed to fondling. He only chooses newcomers and vulnerable females. When approached by a female long-time member of the group, he denies it. He was diagnosed with Parkinson's Disease a few years ago. Regardless of cause, how can he be approached in caring concern to bring about a change in behavior? Does anyone have experience with successfully dealing with this kind of inappropriate behavior?