So fair I've just tried to avoid these people and used them as a reminder of what we struggle against
This basically
People who are literally working for weapons companies aren't going to be easily swayed that their way of life is evil. It's not worth the emotional effort or looking weird in front of coworkers for no benefit.
I think this advice technically makes me a lib according to Mao, but I think he was writing more about fellow comrades than people who should be getting the wall anyway