Call to Action is a heretical movement which opposes two ex cathedra definitions, "Humanae Vitae" and "Ordinatio Sacerdotalis". Of course belonging to them is a grave offense.
What is grave in Lincoln, is not grave in Chicago, or New York, or even in Philadelphia.
Bruskewitz also excommunicated SSPX members.
I'm told on here, every day, even by traditional Catholics who are not in the SSPX, that it's just dandy to go to an SSPX Mass if there's no Indult Mass. And that the Vatican says that's OK.
Now, I don't think it's OK, but, if there's justification from Rome (Msgr. Perl), why would Bruskewitz think this is a "grave offense"?