Very interesting thoughts, with which I partly agree. But I have reservations about other parts.
To say that words are simply sounds and that their emotional meaning is attributed individually, minimizes the real effects that words can have on people. Let's not forget that there is a wealth of research showing that words can have profound and lasting impacts on self-esteem and mental health. In particular, verbal harassment can cause psychological damage comparable to that of physical harassment. I don't think your aim was to downplay this point, but I thought it worth pointing it out.
Another thing, you claim that there are no universally negative words. But what about racial slurs or other discriminatory terms? I think these words are widely recognized in many cultures as hurtful and unacceptable.
On the other hand, yes, we can have control over how we react to words. So we can reduce the impact of negative words, but I don't think we can get away from them.