There are sedes who will not say it is dogma outright, but who act like it.
To them, una cuм is a sacrilegious Mass and a mortal sin to attend.
To them, SSPX and Resistance groups are objectively schismatic, just as the Eastern Schismatics are.
Many will say only sede's are true Christians.
A lot of these errors stem from an exaggerated understanding of papal infallibility.
Fr. Radecki of the CMRI in his catechism says that Encyclicals are infallible, for instance, and Bishop Sanborn treats anything put in the AAS as objectively authoritative and infallibly safe to follow, including Pius XII's Italian, private speech to midwives.
Bishop Sanborn wrote an article entitled "Opinionism", stating that as Catholics we HAVE to solve the papacy question, or else we are not truly Catholic, since our salvation depends on submission to the Pope.
He seems to forget there are many things pertaining to the crisis that simply have not been solved yet by the Church.
I know a sede who is associated with the Cassiciacuм Thesis crowd, and is so intolerant of those from the Resistance or SSPX, that he declared he would simply walk away from such a person upon learning their position on the crisis. Many sedes follow this sentiment as well, and spend an inordinate amount of time fighting with traditional Catholics who disagree with them.
All of this makes me very sad. The devils love it. It is a huge distraction from the interior life and growing in the love of God.