Who is parenting who?

Hi all,
I find it quite scary sometimes that my two year old son sometimes sounds like I do when he talks to me. If I do something that he doesn't like or want me to do at that particular moment (such as talk to my wife, or eat), he will firmly tell me not to do it. He does this using the same language and tone of voice that I use when I tell him not to do something that I don't want him to do (such as hit the cat, or throw food on the floor). And why wouldn't he? This is the way he has learned from my example to handle such situations. What to do, besides taking a vacation?
I accept that fact that my son sometimes talks to me the same way I talk to him, because, like I said, he has learned this from me, and being only two, he doesn't know any other way, besides the ways that I teach him.
But listening to him in these situations causes me to pause and reflect on my own handling of situations where I would like him to stop doing something. I often try now to approach such situations with a different tone of voice, and different use of words.
Rather than saying, "Don't do..." I try and say what he should do. For example: "Don't put the cat in the oven" = old me... and, "Try petting the cat nicely while it is lying on the floor" = new me.
I have read in several books that this is the better approach anyways. Children (and adults too) ignore the negating pieces of sentences (i.e. we ignore the "don't"). For example, if I say to you, "Don't think of a pink elephant," the first thing you do is think of a pink elephant. So when we say to our kids, "Don't draw on the walls," you can be sure your walls will very quickly be many shades of red, blue and purple.
The other big question I ask myself is how often I should let my boy get his way. If he asks me not to do something that he doesn't want me to do, and I don't listen to him, why should he listen to me next time I ask him to "Pet the cat only"? He is still too young to understand that he always has to listen to me "because I am the father and I know better" and I don't necessarily have to listen to him.
So, I try and negotiate where I can. Of course, on big ticket items, there is no negotiation. But on small things, I am open to negotiate and sometimes give in to his requests. I think this helps in the long run, because if he feels that I take him and his requests seriously, he is more likely to do the same with me and my requests.
Definitely something to think about, and I am still honing my skills in this area, so if you have any comments on what has and has not worked for you in this space, please leave a comment!