This topic has been covered ad nauseum, but my response has not changed...why are you only worried about non-Tesla models? Tesla is still putting out way more cars than those other makers, so why not ask how existing Tesla owners feel about having to charge next to all those new Tesla owners that came after them? Isn't it really the same thing?
As long as they've been able to claim value in having the Supercharger network, Tesla has had a responsibility to keep up the rate of expansion of the Supercharger network with the pace of the number of vehicles that have access to it. In that respect, nothing has changed. If they want to open up the network to other vehicles AND claim that they have a pre-eminent network, then they have a responsibility to make sure that the rate of expansion keeps up with those vehicles, regardless of make.
And the good news is that the revenue they earn from those other makes, at least supposedly being more expensive for those makes, will actually enable Tesla to expand the network in a more sustainable fashion.