Slippery slope? It's not a logical fallacy: he very clearly said that they should reconsider the case.
This is what Clarence Thomas wrote: In future cases, we should reconsider all of this court’s substantive due process precedents, including Griswold, Lawrence, and Obergefell.
You don't think Florida and Texas would ban gay marriage, right now, given their current political climate? Really? Are you that naive?