A few of your points don't make sense, because ALL Tesla stations can't become publicly available. They will have to build new stations (or additional chargers at existing stations) with the standard L3 EV connector, not a Tesla connector. So, non-Tesla users can't take up spots at Tesla chargers because they physically can't use the plug.
I don't think this is true. In Europe, Tesla retrofitted a lot of Superchargers (maybe all of them) to have both Tesla (Type 2 in Europe) and CCS2 plugs when they introduced the Model 3. In principle, they could do the same thing in North America, only with Telsa and CCS1 connectors. In fact, there's been
vague reporting that Tesla is planning to use some sort of built-in adapter (called the "Magic Dock") to enable the Supercharger to serve both Tesla and CCS1 vehicles using a single cable. Something like that would probably be fairly cheap and easy to retrofit onto existing stations.
That said, I'm skeptical that Tesla will roll out such a solution quickly. In Europe, they've been doing it in stages, starting with the stations that have lots of capacity, so as to avoid the sort of full-station problems that so many people on this forum fear will completely ruin "the Tesla experience." I have
no inside information, but if I had to place a bet, it would be that they'll do something similar in the US, initially reserving CCS1 support to new deployments (to take advantage of Federal and/or state subsidies) and to stations with lots of unused capacity. They may eventually provide CCS1 at all Superchargers, but not right away.
Going back to the original question, remember that you need not always be a Tesla driver. In a year, two years, five years, or whatever, you may buy a new car, and at that time, it will serve your interests to be able to charge it anywhere, no matter what brand you buy. Tesla adding CCS1 support to Superchargers means that you'll be able to pick between a Tesla, a Ford, a VW, or whatever, without concern that you'll be tied to a particular charging network (or excluded from one). This is a good thing for you as a consumer, even if you as a Tesla-driver-today see no benefit from Tesla opening up the Supercharger network now. Of course, some Tesla drivers today will buy Teslas as their next cars, but being able to cross-shop other brands is good, even if you think today that you'll never buy anything but a Tesla. Some other future vehicle may be compelling, and the competition is good for Tesla. Don't get so blinded by your short-term interests that you don't recognize your long-term interests.
Speaking of competition, this goes the other way. My understanding is that Tesla's Supercharger network is the most reliable of the DC fast charging networks. Thus, opening it to other brands will provide more direct competition, hopefully spurring improvements in reliability and customer experience for EVgo, Electrify America, ChargePoint, etc. This will be a good thing, even for Tesla owners -- with the help of adapters, Tesla owners can charge at these non-Tesla stations, so making them more reliable can benefit us, as well as help make a transition from a Tesla to a non-Tesla in the future easier, should that be in the cards.
