From experience, a couple of precautions can be passed on.
Avoid illustrating a cognitive disability with one or two examples. Every example has been done by a normal person at some time. The folks who want to deny a cognitive disability will tell you when and how in more detail than you have time to listen to.
Avoid educating family and friends in the presence of the cognitively disabled person. They usually listen to parts of the education. If they capture a part that offends their obsolete identity, they may perseverate on that idea for weeks. If so, avoid arguing with them. Arguments tend to build anger and survival defenses.
At the worst, survival pushes people into a fight or flight reaction. Your best action in the middle of that much explosive energy is to sit down and be quiet, then try to think of something to distract them. Ask them about their interests. Stop for a coffee or tea break. After the energy settles down, a calming action or taking a walk may further distract them. Actions prevent resuming the argument. If you find yourself in the middle of one of these scary messes, you can take charge and work it out, but it may take two or three unplanned hours. After the energy level simmers down, you will probably need to make some phone calls to re-organise your schedule.