A good point is not
lost by being polite. Rather, a good point is more likely to be absorbed
if it is put in a tactful manner. Moreover, someone who is polite is more able to engage in a two-sided conversation
with people, where the whys and wherefores of both the pros and the cons can be explored in far more in-depth manner than being rude.
But since both of you have yet to learn that, then I'm afraid you're not going to be likely to enjoy such a pleasant experience with people--the only actual two-way conversations will be with people who will reply by getting into fisticuffs, which I shall sit back and enjoy greatly, to see the two of you getting a taste of your own bitter medicine.