In our day to day lives, magickal or otherwise, we constantly infuence others' free will. It is somewht naive to pretend we don't. We persuade, we pressure people, we emotionally invest, - constantly. We all act in an ultimately selfish way. We behave in such a way as to gain a favorable outcome for ourselves. Don't deny it, it's true.
We behave in such a way as to be popular, to be acceptable, or to be respected. These are all behaviours that influence the free will of others, albeit subtley. This is our social nature. Then suddenly, we go magickal! Suddenly all of these things are now wrong!
Forget it. We are social animals, and that will reflect throughout our whole lives, which includes our magick. I doubt it is even possible to live without influencing the free will of others.