Disclaimer: this is not an attack on you personally.
I think this attitude is part of the problem with transportation in this country. Transportation systems benefit the entire society. This particular issue, train from Orlando to WDW, doesn't benefit Disney as much as it would hurt Hertz, Enterprise, Alamo, Dollar, etc. Disney would still get their visitors.
You (we all) actively pay for the highways and roads in, whether it is through tolls on a toll road or through your taxes. You pay for your state's airports through your taxes (and hopefully they eventually become relatively self sufficient). Orlando International Airport, for example, used to be McCoy Air Force Base. McCoy, it's runways, infrastructure, etc, was paid for by taxpayer money. The conversion to the passenger airport we know today was paid using city funds (taxpayer money). Yet, no one complains about that. Where is the outrage for the wasted money on the boondoggle that is air travel?
Similarly, many western countries in Europe have extensive train, airport, metro, and road systems. There isn't outrage there. The money isn't wasted.
Disney pays federal and state taxes, so in a way, their money does help pay for the transportation system.
These things, roads/airports/rail systems, all benefit society, improve commerce, etc. A rail system, if comprehensive enough, would work.
It is, however, important to remember that it is all part of the United States' transportation system - a system that includes air travel, interstates, local roads, metro systems, Amtrak, rental cars, taxis, etc. Its a system of systems, and all need to play together. These systems in the US don't play together as well as they need to. I would love to be able to fly to Tampa, take a train to Orlando, rent my car at the train station, and be on my way. Right now those things (flight to TPA, train from Tampa to Orlando, and rental car) likely aren't planned to be connected. This country needs major train lines to service our major airports, etc.
This right here is the issue, not "if Disney wanted it, Disney should've paid for it..." Try telling yourself that same argument next time you drive on I-4...for "free," or the next time you need the police or fire department.
BTW, I am expecting some hate for this post...so no worries. I'm a big boy.