Convincing 10 people to CONSISTENTLY AND FOREVER decrease their meat intake by 10% is the same as convincing just 1 person to go vegan (aka 100% reduction).

I don't think so. 10 people reducing it by 10% is nothing in a society where everyone claims they have reduced it and only eat happy to be killed animals from their uncles farm. On the other hand one vegan could show hundreds of people that there is no magic to not abusing animals and change some. It is not only about the personal impact but when veganism hits a critical mass and changes society.

Vegans, even life long vegans, exist. We do not need meat

I know lifelong smokers. The human body is resilient. If your argument is that veganism is healthy, you need a lot more than "I'm vegan and I'm not dead".

I mentioned elsewhere about protein intakes. It's not a controversial take that protein is one of the most important things we need in a day, that protein is easiest to find in meat, and that our body isn't as good at digesting plant protein. For the rest, telling someone to go plant-based when you need a lot more than just a multivitamin to hit the Iron and B-12 content you need.

Whether or not veganism can be healthy (it might be), it is a known quantity that naive veganism is absolutely unhealthy. So my problem with "getting them vegan is easier than getting them to cut 10% meat" is that you're trying to create naive vegans. That means you're trying to create smokers.

Considering half the country threw a temper tantrum over being asked to wear a mask during a respiratory pandemic, I don't think you're being realistic in your view of everybody being able to go vegan. Many of these people threw a fit over AOC "wanting to take away your cheeseburgers" even though that wasn't what she was proposing; they just knew that it would rile up the rural base.

I think it's much more reasonable to convince people to make two easily implemented changes: no more meat at breakfast, and meatless Mondays. With these two easy changes, only 12 out of 21 weekly meals is eligible for meat, which is a ~43% reduction. Not everybody will do it obviously, but the same people willing to cut 10% will probably cut 43% when presented in this way. Especially if you bring up the financial cost, health risks, and storage inconvenience of buying and eating so much more meat than is necessary.

I also think it's a little silly to say that it's easier to go vegan. You need to study food labels and nutrition facts to see if there is some animal byproduct involved. When you go out to eat, it's not always clear whether options on the menu are vegan friendly, but restaurants are getting better about that nowadays. But I think you're also assuming that people have the means to always choose a product that may be significantly more expensive. I think you'll have better luck convincing people to occasionally think about whether their stirfry really needs steak or if mushrooms are actually enough to carry that earthy, satisfying bite they're looking for this time.