Some people are impolite. That will never change. The internet somehow brings out the worst in some people. Mudcat is worse than most discussion forums because the owner has decided that editing must be very light-handed and only the worst, most egregiously offensive messages will be deleted.

We have discussed this topic to death, and no matter what we say, the impolite people won't change their habits and won't go away. Arguing with them only makes them worse. The best thing to do is ignore them. Note who the impolite people are and don't respond to them at all.

Try not to let them discourage you. You will find plenty of other polite friendly people to discuss things with.