I think the purpose of the tax credit was to invigorate the electric car industry. I would imagine any way that Tesla can use the tax incentive to move more cars is in line with the government's intent.

Increasing sales makes the company better able to produce electric cars for the market, which I argue is the ultimate reason the government created the program. I don't see this financing option as screwing anyone any more so than a normal purchase that takes advantage of the tax.