Is it possible to be "positively prejudiced" against one group without also being "negatively prejudiced" against one or all others?

I'd say it's possible, I wouldn't say it's very common though - in my opinion the majority of progressives are guilty of hypocrisy in this respect.

If everyone was racist we'd be living in apartheid. Frankly, there is no political coalition willing to push apartheid because a plurality of people aren't as racist as some people in this thread seem to think.

What if there was a system that achieved the same effect as apartheid, without requiring an actual apartheid law? Do you think that would be better or worse?

Well that's certainly the intent of some bad policies passed under cover. But generally speaking if you shine a light to those policies most people will be against them.

I concern myself a lot with these kinds of “shadow caste systems”, so I’m intrigued by your faith that they are universally opposed.

I see a lot of people who sort of cultivate a barrier of ignorance because their bread is buttered by the system. They do their job but, only semi-consciously just won’t peer behind the result of their actions.

So I will meditate a little on your position. Maybe I’ve got the wrong bias here.