Exclusive to whom?
Certainly you did not expect Superchargers to remain open only to you and everyone who bought a Tesla prior to you (i.e. cut off access to the Superchargers to everyone that bought a car after you). If you were okay with the fact that people that bought a Tesla after you were allowed to use your Superchargers, does it really make a difference whether the car they pull up to the Supercharger in is made by Tesla or some other company?
Granted, I do think Tesla, or any other network provider, needs to ensure that chargers are operational, available, and reasonably convenient for people to use. If that means by opening up to a larger set of users (either by building a crap ton more cars than they did back in the day, or providing an adapter/connector for other vehicles to use), then they should be prepared to expand the network to support those users.
And this is precisely what Tesla is better able to do by charging a premium for access to non-Tesla users. It should help pay for even faster expansion to keep up with increasing demand than would be possible if all the users were Tesla users and paying $0.10/kWh less for use.