Just because there are some bacteria that are already resistant to doxy doesn't mean that shifting the entire ecology of human bacteria so that resistance again

Just because there are some bacteria that are already resistant to doxy doesn't mean that shifting the entire ecology of human bacteria so that resistance against doxy is selected for is a great idea. If you have a garden and use pesticides, there are probably some weeds that will be resistant to it. But the mere existence of resistant weeds is not an argument for continued indiscriminate use of pesticides, as you will end up with even more. Degree matters.