Its not true this nice guy vs tough guy thing. My H is a nice guy and thats why I love him and because I love him thats why I lust for him. So don't stop being nice.
About your arguments, I don't think your W loses respect for you if you don't argue back. I'm a bit like that in this respect. Whenever I'm in an argument, I have all these things on my mind that needs to get out and I can't let go of them until its all trashed out. This is very unhealthy of course. My H often backs down from an argument but I do not lose respect for him. In fact I respect him more for being more in control of himself than me but like your W I cannot let go until he argues back and then I feel worse afterwards. Oh well, sometimes people are too emotional for their own good. LH