Avoiding publishing in a particular journal without bringing up politics
The other answers are focusing on OP's particular ethical stance, but I think this question deserves a somewhat general answer, so here goes:

You are essentially asking how to take a political stand without involving politics. This is impossible unless you hide your motivations for wanting to avoid this journal--as you've already tried without success.

You just have to decide whether you feel strongly enough to state your beliefs out loud, at least to your advisor. If you don't want to publish in this journal under any circumstances, even if it means taking your name off the paper, so be it, but be prepared to face the consequences of that. If your priority is not rocking the boat with your advisor, so be it, but be prepared to have your name associated (at least a little bit) with the journal. It's up to you how much that matters. A middle ground would be raising your objections with your advisor but leaving the decision up to him. This is about your personal ethics, so no one can tell you what the right choice is.