> the argument for comparative advantage has nothing to do with the redistribution of income
But it has.
Comparative advantage shows you that the country as a whole can afford more with free trade than before.
But one of the theoretical consequences of the Heckscher-Ohlin trade model [1] is factor price equalisation, ie in once country wages might fall while returns to capital increase. Inevitably, there are winners and losers.
Now, since economics rightfully shies away from inter-personal utility comparison, that does not tell you whether the country as a whole is better off; unless you invoke redistribution, such that everyone has at least as much as before (now you can say that everyone is (weakly) better off, and some strongly, and thus the country).
This is well understood (see eg [2] for some more on this issue, quoting James Kwak, & I'm pretty sure Krugman has articulated the same). (This, btw, is not an argument from authority, but an answer to "I don't know where you got the idea")
> Of course there are economic winners and losers, but by attempting to fully protect everyone, everyone becomes a loser
How about comparing to northern Europe, and not some dystopia nobody is arguing for anymore?
My point was that the case for free trade is good and valid, and it rests on (and should go along with) redistribution/compensation.
[1] https://en.wikipedia.org/wiki/Heckscher–Ohlin_model
[2] http://www.samefacts.com/2015/05/everything-else/free-trade-...