How do you convince someone of the value of egalitarianism?

An odd question to ask, I'll admit, but I think it's worth asking.

It's hard to have a public conversation today about political or politicised topics because people will pipe up and tell you that you're crazy and your ideas are completely backwards. And the reason why people say this is often driven by conflicts between personally held values rather than the ideas themselves. As a result, these conversations usually end up with both sides arguing past eachother and no concensus is ever made; nobody is happy.

One of the more common reasons for these arguements is typically because one party believes in egalitarianism - the belief that all people should be treated the same - and the other one does not. It's particularly strange to see given that so many countries have egalitarianism as a cornerstone to their government and laws. Yet we still see many people trying to take away rights and freedoms from certain classes of people.

Regardless of any particular conversation, what do you think is the best way to convince someone in the value of egalitarianism? How do you convince someone that they're not part of a higher class who has power over another?