They think factory farming practices are morally bankrupt… but they like eating meat.
As a Reducitarian, he won't buy or order meat for himself… but if he's served it he won't complain.
This helps reduce his own use of meat structurally without being a huge inconvenience in his life.
But the more people that do this, the less meat use there will be, at a super-linear rate.
Because Reducitarians won't serve others meat, either.
The likelihood a Reducitarian eats meat is tied to how often they eat meals served to them by someone else, and how likely that other person is a Reducitarian or a vegetarian.
So if the other person is more likely to be a Reducitarian, then the likelihood you don't eat meat goes down: a multiplicative effect.