It's not as much fear of optics as not giving an easy win. And they actually are not democratic socialists. Their policies and statements align far more with social democracy.

They are not socialists if you look at their policies and statements. Socialism seeks to overthrow capitalism, either democratically or by force.

Ignore them if you want, but they won trump the election. For example just the Latino vote alone was a huge jump towards Trump. They had it with identity politics and aligned with bread and butter economic issues, and they generally abhor socialism, so there's that.

Ok you didn't define the difference, so I will. Bernie Sanders is a social democrat. He does not want to abolish capitalism.