I believe the attacks on Dr. Plinio and Atila (slavery, cult, Plinio's mother, etc) are taught in the SSPX seminaries. A direct smear campaign, no, but I do believe there is an indirect one. One thing is clear, SSPX does not like TFP, TIA, Plinio, or anyone else.
When I was in the seminary, TFP was barely mentioned. If they mentioned it, it was only in passing. In general, they were not too favorable, but not overtly hostile either. More like they didn't care that much. +Williamson was ambivalent, not sure.