Then why are we taking offense to the phrase? Worse yet, why are we taking offense to the phrase despite knowing that the alt-right wants us to take offense to the phrase because most onlookers will see it as anti-white (which is a reasonable conclusion, for the overwhelming majority of people that don't follow internet culture).

These things being true does not imply they are relevant. "It's ok to be non-white" is true and poignant social commentary, and thus I value it for the latter. The truth in it is necessary, but not sufficient. "It's ok to be white" is a fact, but it is simply a fact. It is nothing more than a fact.

>why are we taking offense to the phrase despite knowing that the alt-right wants us to take offense

I'm not taking offense to the phrase, I'm taking offense to the willingness of someone to say it where it is unwarranted. The phrase is not offensive. The willingness and desire to offend is. Exercising that willingness by employing an otherwise true statement is both offensive and cowardly.

In any case, I do not make decisions based on the whims of the Alt-right. What they want and what I want are not going to be intentionally correlated or anti-correlated.