We all parent by example, one way or another
Go and sit at a busy park and people watch for a while, and you’ll probably notice something. Parents who scream and yell at their kids usually have kids who scream and yell back to them, or to other children around them. If parents continually treat others with disrespect, their kids will too. Learned behavior is always being learned, bad or good.
In contrast, watch the parents who treat their child with respect and kindness, and you’ll see a child who will treat others the same way. Kids watch their parents, and this is how they learn the ways that adults should act.