Fr. Grosso is not with any of the resistance priests. He is with a group that attacks the resistance as far as I know. The same goes for Fr. Meramo
Fr. Méramo started to resist Bp. Fellay's betrayal long before any of the commonly considered resister priests? Who dare to say Fr. Méramo is not part of the so-called resistance. Who decides who is and who is not part of the so-called resistance?
Even Bp. Williamson had to admit that Fr. Méramo and some others were resisting Bp. Fellay´s betrayal before he and other priests started to do it.
Fr. Méramo was expelled from the SSPX in 2008 or 2009.
Fr. Grosso decided to join the so-called resistance in 2010, and the group you refer to does not attack the resistance, but disagrees in many things with many priests that resisted somehow Bp. Fellay.
So, again, who decides what the resistance is and who belongs to it? Fr. Pfeiffer seems to disagree with Bp. Williamson and Fr. Zendejas. Fr. Meramo and Fr. Ceriani disagree with Bp. Williamson. Bp. Williamson seems to accept Monsignor Patrick Perez, who most probably is not even a valid priest...