I appreciate your point and I learned something new from it, but I disagree with the last part. By your GP's own admission, pesticide overuse doesn't threaten all of humanity like antibiotic overuse does. So no, they are not "as right as" someone trying to avoid contributing to the antibiotic overuse problem. Not all problems are equally important.

He would be wrong because animals grown for meat also eat vast quantities of of plants, which are of course grown with pesticides. So eating a plant based diet reduces the amount of antibiotics AND pesticides used globally.

Bioaccumulation of pesticides in animal tissue is a serious problem.

I do not think you can ever consume the same amount of pesticides by eating plants if before that you ate nontrivial amounts of chicken, chicken eggs, beef, milk etc. Cow eats several tons of plants in its lifetime. I'm pretty sure human comes no where close. The bioaccumulation happening there is a serious issue.

That stuff is filled with bioaccumulated pesticides.

> I expect this is true but it is not going to happen.

What is your point. That we shouldn't do anything, because it is all hopeless?

> Or is it that the problem would be greatly reduced if everyone stopped eating meat. I expect this is true but it is not going to happen.

This is a classic Tragedy of the Commons. No single individual is incentivized to sacrifice for the good of the group as a whole.

But it's not correct to say that "it's not going to happen" - there are many counter-examples. The most notable is the ozone layer depletion problem that has been largely mitigated over the last 3 decades through concerted action among govts, NGOs and with public education. From https://en.m.wikipedia.org/wiki/Ozone_depletion:

"The Montreal Protocol is considered the most successful international environmental agreement to date. ... The ozone hole was seen as a "hot issue" and imminent risk as lay people feared severe personal consequences such as skin cancer, cataracts, damage to plants, and reduction of plankton populations. ... Americans voluntarily switched away from aerosol sprays, resulting in a 50 percent sales loss even before legislation was enforced."

So yes, at some future point, if govts/NGOs do their part and the average human comes to believe they face imminent personal danger (which we already do but it's hidden), meat production may well become heavily regulated and large numbers of people may switch to vegetarianism.