Bill, I’m afraid offence is the price of free speech.  I get offended every day but I wouldn’t want to curtail reasoned discussion.  I suspect you don’t either.

I think you overestimate the level of education of the Catholic laity—and by education I mean catechesis in the basics of the faith, not the number or level of degrees.  Most Catholics, especially younger ones, are completely unfamiliar with the basic tenets of Catholic moral theology, including matters in the sexual sphere.  They haven’t heard any discussion of divorce or of contraception, which are rarely mentioned from the pulpit.
Thus, were Fr M speaks to speak at a Catholic institution, we couldn’t blame them for thinking his statements are in line with church teaching.  In fact, they’re not.

There’s nothing to prevent Fr M from speaking at a local ECUSA or UU church.  But it’s misleading for a Catholic institution to give him a podium.