Actually they can if they wanted to as
@MP3Mike pointed out that thay even blacklisted a car for leaking fuel. As he said, the title status of a vehicle is not a protected class. Businesses can refuse service for practically any reason, as long as they aren't discriminating against a protected class.
Edit: also up thread someone detailed working with a lawyer for years to try to fight Tesla's salvage blocking policy and didn't end up going anywhere, which is even more evidence what you say about what Tesla is doing being illegal isn't true.
I'm sure some Tesla owners would love that as they don't want people competing for chargers. On the government end, all they would be doing is shooting themselves in the foot as Tesla opening up their network is pretty much the biggest game changer for non-Tesla charging in a long while.
No it doesn't, as pointed out earlier, allowing non-Teslas to charge (due to impossibility of implementing a salvage block) does not change the blacklisting justification at all. If a Tesla caught on fire at a supercharger, it'll be widely reported and the media will practically never bother to find if it is salvage or not. If a non-Tesla caught on fire at Magic Dock, the negative impact on Tesla would be far less or non-existent, given it's not a Tesla.