No one has offered their opinion as an absolute. I don't think anyone here feels that "professional training" is necessary for the expression of their opinion or that those who have "professional training" are to necessarily be considered as infallible.
You don't seem to feel a bit restrained or "bullied" in expressing your opinion. Why do you think others are feeling that way?
"If more people felt free to express their opinion..."
I see lots of people here expressing differing opinions. They don't seem a bit inhibited by anything. The people here seem to me to be folk who think for themselves and don't cower in a corner if someone says something they don't agree with. They say what they think - even if it means someone else may come along afterwards and accuse them of "bullying" others if they express a point of view that person doesn't care for.
By the way, do you do colonics for a living? Are you a professional in that? If so, one could wonder if that's why you have a particular antipathy to anyone saying anything negative about them - right or wrong. If you are not, should you be giving your opinion if (?) you feel that only professionals should be listened to on this topic?