I have observed this personally. I grew up in an SSPX chapel and my family left because a priest kept making up excuses to deny some of us certain sacraments (the chapel had a nasty political situation). We went to the startup FSSP chapel for a few years. When I reached adulthood and tried to socialize with some of the people I was shocked at the sheer animosity towards the SSPX. Most of it was from former Novus Ordo Catholics who, in an effort to "fit in", started dressing like American 19th century protestants, rejecting modern medicine, and reading up on geocentrist and flat earth conspiracy theories. These same people held on to the belief that Lefebrve and Fellay were stubborn schismatics, all SSPX confessions were invalid, and that my Confirmation at the hands of an SSPX bishop somehow did not count.
You'd think the FSSP would be warmer to the SSPX, but some of their priests have a serious case of ultra-ultramontanism that they try to reconcile with traditionalism. Some FSSP faithful want to strut around with a superiority complex over the "Novus Ordo" Catholics while simultaneously doing the same against the "schismatic" SSPX. It just doesn't work.
That said, I've known many good priests and and not so good priests in both fraternities. We always have to be careful not to over-generalize.
:cheers: