Why do people feel the need to demean others to feel better about themselves?

You've sort of answered the question already. It's to feel better about themselves. When they point out the flaws in others they take the attention off of their own. They want to bring people down to make themselves higher. It's also about a sense of control. Once they realize that they can make people feel as low as they do, they sort of feed off of it. It's a coping mechanism, no, not a healthy one. But it makes them not feel as insignificant. I find that a lot of "bullies" have had little control in their life and/or have rude or controlling parents. Since they have no control and are belittled by their family, the only time they feel worthy is when they make others feel worse. It's kind of sad, but it starts a viscous cycle where hate only breeds more hate. Most bullies don't actually think they're better than everyone, it's that they are so insecure and feel so small that they try much harder than needed to assume some sort of dominance. A lot of bullies deal with a lot of self hatred and end up taking it out on others.

There are two different types of insecure people; those that put others down to help themselves feel taller, and those that try to build others up, hoping that others will do the same for them. I suffer from the latter, and it's exhausting being a people-pleaser, but I'd rather be a sad people-pleaser than to be a sad bully. I'm not trying to make being insecure appealing, but I'm trying to say that while I'm working on building my confidence, I would like to avoid tearing down someone else's confidence. The people that demean and hurt others to make themselves feel better struggle much more with insecurity, because they refuse to acknowledge that their actions are a result of being insecure. Confident and happy people don't give a crap what other people think, if other people are more successful than them, or what people do with their lives, because they are too busy being happy with their own lives to waste their time caring/thinking about the "faults" or "defects" of others. The best way to deal with those that demean you, is to kill them with kindness and to keep a poker face of confidence when you are around them; it slowly kills them to think that you are not phased by their words, because that just further reinforces their insecurities.

Some people feel the need to demean others for their own self esteem because they like to believe that they are superior to others, and that they can always 'get one over' on the other person. The person may have low self esteem themselves, thus they attempt to demean other's self value to raise their own self standards.

Putting others down is what all humans do, I've done it a few times. I don't think it's always about feeling better about themselves, rather than want to feel empowerment. I've gotten bullied before and to make myself steal back the confidence that was ripped from me form others, I put down my younger brothers. If you're getting put down by others, try to tell someone about it. :) It helps a lot to get it out so that you don't have to turn around and make others feel bad. :)

Insecurity, depression... it gets the best of the people that suffers from it... don't ever condone it, though, be there to help, but never become the emotional punching bag of verbally abusers.

Some people feel the need to demean others to feel better about themselves because they seek attention which they don't get elsewhere. They might also be hurting on the inside and demeaning others is their way of coping.

It's because of their own insecurity. If someone feels insecure about themselves, they tend to try to find a way to assert some form of dominance. By demeaning others, they feel that they have power over another person, masking their own feelings of insecurity.

It tends to be due to the enviroment that the person has grown up in. Not just necessarily the area but family and relationships could be main factors.

They take their own unresolved issues out on others. They are hurting but they don't want to admit it to others but most importantly to themselves. Unless they choose to resolve their issues they will never heal. I hope they can heal. If they are too hurt that they can't don't take what they say personally and choose how you react to them.

They think it will take away the hurt and shame they are experiencing from their own life or past and by putting others down, they think it'll help them get past that.