Yes, you can change someone.
Seems I disagree with most people. A refreshing change where most people believe it is morally wrong to want to get someone to be a better person. Can you get an arrogant person to change?
Yes, you can change people. Yep, I said it. You can change people. And people are changing people all the time. It is called leverage, pressure, finding their current motivation, etc. etc.
Sales people use it all the time. The media does it as well. Everyone is changing things all the time. People discuss, learn, grow, adapt constantly.
How many times have you changed your mind today? What influenced you - just you? Or were there any external motivations used by others? Was the media involved in any way online or offline?
Did you turn on the radio and instantly like the song playing and felt better? There are trillions of dollars spent every year, millions of jobs where people spend all day - every day - planning in exquisite detail about how to change things to their own advantage. They are called politicians, lawyers, corporations, and even Reddit, Quora, and others.
This also applies to motivation. Can you motivate someone? Yes, see above.
Everybody begins the desire to change once the proper form of benefit is shown to them. Everybody begins to desire to change once they see a better way of getting what they really want. An arrogant person (generically speaking) wants to be right and known for being right. But what is wrong with being admired, appreciated, respected, and revered if the person keeps their ego in check about it. People love compliments. Once an arrogant person sees this better way of getting admiration and appreciation they want to change.
People often say change yourself first. I agree and add this - Change yourself first so you can change others for the better. Or rather, learn the skills of leadership, self improvement, and how to offer a better way to people.
But can people really change? Most think no. I disagree again (respectfully). I have just given an example about how sales, marketing, and motivation combined with psychology and personal development can produce the desire to change.
After all, isn't that what this very site is all about? Marketing to change people?