Does shit people come from shit parenting?

Why do you think some people are nasty, uncourteous, rude, mean, selfish, inconsiderate, lack morals, ethics, etc..?

Is it because they were brought up that way? Was it their parents, environment, experiences or all of the above that taught them to be that way? Which institution ultimately has the most power in dictating how well-rounded people will become? Do parents have the FINAL say?

Do you consider yourself a good/bad parent and why?

Let's keep this under the assumption that the child is being raised in a household with two parental figures. Let's exclude the extreme scenarios for the sake of keeping the conversation on track.