I'll quote you just as an example.
It most definitely is not a moot point. You're right in that a player needs to be of some standard and the better the better.
However, if you have a right footed and a left footed CB, it's better than if you have two right or two left footed ones. Neither of them plays in the center so that it wouldn't make any difference. If a player is far superior, he can play on the wrong side too, but it's not ideal, as someone has mentioned. I wouldn't want to play Vlaar on the wrong side if possible. But if Okore is clearly better than Clark, I would.
I don't have evidence he is at the moment, so I'd play Clark on the left and Vlaar on right. Let them fight it out. No way is it clear that Okore walks back in and Clark gets dropped.
I don't get it either. If a right footed cb needs to go on the left side of the pitch is he a lesser defender all of a sudden? Most players today are at least reasonable (if not good) with both feet, I wish somebody did a statistic on Vlaar's defending touches on either side the pitch to see exactly if this 'right/left footed' discussion has any relevance
I have a statistic.
When Vlaar is forced out of position to accomondate Okore, we lose 100% of the time (sample: 3 games out of 3).
It's only natural, that Vlaar won't deal as well with crosses coming in from the left than from the right. As he is right footed.
The question, imho, is, if Clark + Baker is a better option than Okore + either Clark or Baker, in the unfortunate situation Vlaar is not available.