I am aware of a reform ‘convert’ in my city who travels often. He is in his early 50’s. He lets himself get counted for minyan in several orthodox synagogues throughout the country, and even gets called up to the Torah there. I feel the need to speak up, but at the same time I don’t want to engage in lashon hara. What would be the best way to deal with this issue?
Based only on what you are writing, if it is indeed true that he did not have a valid conversion, then he is considered a goy and there wouldn’t be a prohibition to speak about him.
Chofetz Chaim 8