I would be interested in the reasons cited by current prelates for suppressing the Tridentine Mass (indult/non-schismatic) and non-schismatic Catholic traditions. It cuts both ways - liberal extremism forces many Catholics to search for alternatives for worship. In some cases, tragically, this has led Catholics into Protestant fundamentalist extremism.
They are against it, but I don't know a specific "excuse." Many bishops seem to approve it only as long as only older people go. They don't want any young people there. In Hawaii, the bishop allowed an indult, but he made the petitioners promise to "keep it a secret." So, even if you called the chirch,they wouldn't tell you about it.
Another interesting inquiry is the suppression of the Uniate Rites in the USA. That happened long ago (well before V2), and still has resentments in many ethnic communities.