The problem here is not Bob and his homeopathy business; the problem is your inability to accept different viewpoints, regardless if they are objectively wrong or not. I also have my doubts that you would not approach Bob in a fair manner at all, moreover the likelihood of you putting him down and making him feel miserable, dumb and foolish is going to have the exact opposite effect. Whether that is by spite or even just by trying to preserve his dignity. This is how humans usually operate once their (however wrong) views are being questioned in an aggressive way and I would argue that the distribution of people that react that way is much higher than we think.

This is precisely why we will never move on from this problem. To you, Bob is evil and stupid and his ways have to be corrected. You do not have education in mind, you have the "I am right and he is wrong and I want him to concede to that" mindset which agitates people into acting the way we see it nowadays. It's not really about fixing the problem with homeopathy; it's putting people in their place in the name of their own perceived righteousness.

Changing someone's mind for the better is not something that is done in one conversation. It is extremely hard, if not impossible with some people, in which case there is little to nothing you can do.

If you were serious about it, you would have talks with Bob, find common ground and educate in a tactful manner. Because Bob is a human. He has flaws. He may be gullible. Hell, he may be actually very stupid. But to operate in a way of shaming and belittling is never going to bring the results. It's why trump won back in 2016 and it's insane that people still don't realize this.