The other point you miss is that average fans don't root for the P5 to destroy the rest of the athletic programs. A Michigan fan might want to see tOSU's athletic program burned to the ground, but that same Michigan fan knows people that went to EMU, CMU and WMU, and may have gone to one of those schools himself. He doesn't want to see them hurt, or he is at the least indifferent. He is certainly not rooting for their demise, as you seem to think.
So Senators are not going to line up to destroy their second tier programs just because Alabama wants it to happen. Frankly, most of them would prefer more schools in the mix than less.
We'll have to agree to disagree about this. You're phrasing it as "rooting for the demise" of non-power schools, but what I see is indifference. Believe me: the average sports fan in the State of Michigan will absolutely let EMU/CMU/WMU wallow in obscurity if it means more national championships for Michigan in football and Michigan State in basketball. They already know that the MAC schools won't ever compete with the Big Ten schools (and people in the South know that C-USA will never compete with the SEC and ACC schools), so it's doubtful that they'd see any purpose of taxing their own home public universities where that money is going to be spent in Washington as opposed to Ann Arbor or East Lansing.
This leads to the other point: it's not as if though taxing the Alabamas of the world suddenly means that money gets shifted from Bama to UAB. If that were the case, then there *might* be some populist support for government taxation of university athletic departments, but that is clearly NOT what would happen. Instead, that money is getting shifted from Bama to those "evil tax and spend liberals that keep infringing upon states' rights" in Washington, DC. Outside of the Northeast (which generally doesn't care about college sports except for certain pockets), I'm not seeing any viable political support for that position. I think you greatly overestimating politicians' aptitude to allow for a single penny of taxes assessed upon state institutions so that it can get transferred out of their own home states to Washington, regardless of whether we're talking about public university sports or, even better, university-run medical centers that actually generate way more revenue than even the largest athletic departments. (Take a step back and think about that one - how many universities are going to be willing to open *that* Pandora's box regarding medical center revenue? The UABs of the world that don't have big athletic departments but take in hundreds of millions of dollars in medical center revenue that generate immense paper profits aren't exactly going to be in a rush to start distinguishing what are "for profit" ventures at non-profit universities for tax purposes.) At the same time, I think that you're greatly underestimating just how much more popular the power schools are within their home states in every region outside of the Northeast - there's just no comparison. Taking money away from SEC, Big Ten, Pac-12 and Big 12 schools to send it to Washington would certainly be political suicide for any politician from those states.
We're not even getting into the logistical fact that this Congress can't get even widely popular bills passed these days due to partisanship and special interests. Good luck trying to find a filibuster-proof majority (as getting 50% plus 1 vote means nothing in Washington since those types of bills don't get to floor no matter which party is in charge) to support a measure that's going to be inherently unpopular with a group with a LOT more power, influence and passion (the power conferences and their respective home states) versus a group that have a lot fewer supporters with a lot less passion by comparison (the non-power schools in general). The NRA leverages a lot smaller group based on passion alone to shoot down what are otherwise widely popular bills (as the problem is that the popularity is with people that are a lot less passionate about the issue and they don't have any centralized lobbying power... unlike, say, hmmm... the Association of American Universities that the Big Ten kind of thinks is important and a majority of its members are power conference members).
Trying to argue that power conference schools should be taxed is an even worse false hope for non-power schools than the misguided wish for an antitrust lawsuit. Anyone in the non-power realm right now should only concentrate on rising up to meet the new standards that are going to get put into place. If the last two decades of the Bowl Alliance and BCS should have taught anyone anything, it's that outside help isn't coming (and anyone that waits around for outside help is going to get steamrolled into irrelevance).