Why is it that I pay $7,500 more in federal taxes for riding my bicycle to work than someone who purchases a $70,000 luxury car? Why don't people who don't even own a car in the first place, and take the bus to work, get that tax credit? We're basically transferring wealth from the middle class to the wealthy by offering these sorts of tax credits (at least, in the case of Tesla; other manufacturers like Nissan are offering more affordable electric cars that are actually within the price range of the middle class).
By offering a tax credit to people who buy electric cars, yes, the average taxpayer is still funding Tesla.
Now, the carbon credits are another issue. I think that those are somewhat more reasonable; you are making the manufacturers of vehicles that have substantial negative externalities fund ones that have significantly less.
Again, though, I wonder why only other automobile manufacturers are able to sell these credits; it would be nice for, say, bicycle manufacturers, electric bike manufacturers, public transit systems, and municipalities which build infrastructure more suitable for living without cars to be able to sell credits as well. Only allowing automobile manufacturers to be in the game means that you are still supporting transportation that requires each individual person to haul around a couple of tons of metal with them for 20 or more miles a day, taking up lots of extra space for storing them both at home and at work, leading to congestion and the necessity for more money to go into infrastructure.