Doctors are not God and they don’t know everything. It’s called “getting a second opinion” because it is an opinion. You don’t have to do what they tell you to do just because they said so. Educate yourself. Spend some time researching. Ask questions.
If a doctor doesn’t have time to explain things to you, speaks down to you or otherwise makes you feel stupid, find a new doctor ASAP!
This article is long, but well worth reading. It talks about the delay between what the science says and what doctors are doing (like what we are seeing around eating plant-based).