Do you find the word lame offensive when used as a synonym for something negative?

No, it's one of those terms that's still socially acceptable to use when describing something that you find unsatisfactory. Actually I haven't heard it used in it's traditional definition in many years, these days it seems that people use other adjectives to describe the mobility-imparied than "lame". I admit I use the term "lame" when descibing something that didn't live up to expectations like a movie I thought was going to be better than it actually was.