I agree, but the legitimacy of majority is significant here as it tends to be premise of left-wing ideologies and also is currently the leading paradigm.

If ideology states that transfer of wealth is okay, and then you argue that you should also agree kidney transfers by the same logic, you have a straw man if de facto the ideology really doesn't agree that. In that case premises of the ideology you used would be wrong. To make a valid argument you would have to formalize the real premises that agree with reality. If you can show incoherence in those premises (compared to some moral framework or the ideology's de jure premises), then you have a valid argument against the ideology. In this case you could criticize democracy as a valid way of governance. I never claimed majority's opinion is what makes transfer of wealth really legitimate. In our system it just happens to be enough and makes a difference. The two others were my main argument which stand regardless of democracy, albeit enforcing them without similar system is probably not possible.

Edit: You can remove all points with (3) and (iii) and the argument is still valid. This actually was the format I was originally writing.