Absolutely, people's interactions with each other are informed by the way the other person is reacting (aggression is a really good example of this). But I don't think that one can necessarily get past existing preconceptions/structures on the other person's part just by doing that; certainly not in the short term.

That people can consciously override subconscious expectations/beliefs/etc, that they can decide how to treat other people rather than just letting the animal instincts take over.

Yes - and I certainly don't think that "it's subconscious" or any such argument is a get-out clause. I'm all too painfully aware that I carry a bunch of my own preconceptions and stereotypes around, and that I don't always catch myself at it; but when I do I do try to bash them on the head a bit.

It's tough though because one of the ways in which humans make sense of a large and complicated world is by using stereotypes (both for their own reactions and when categorising input) and creating structures for people and situations. That process is going on below conscious level, so almost inevitably any work on fixing it has to happen after the fact. Which is difficult. A surprisingly large amount of behaviour is stereotyped (which is why habits are so hard to break - it's going on below the volitional level to at least some extent), and that includes interactions with others.

It's still not a get-out clause, though.