Frankly, Bernie is taking the right approach here. You cannot allow yourself to be the "other" in the minds of some people. As soon as you are, logic flies out the window and it doesn't matter how close you may be on a whole host of issues, if you're not part of the tribe you're the enemy.
Think of gay acceptance and gay marriage. Hugely unpopular for a long time, but as soon as people started to see that "the gays" were a part of their own tribe, opposition swiftly collapsed with no real meaningful opposition left on a state or national stage (and in many ways, across the world with notable exceptions). "When people recognize that its their son, daughter, brother, or sister and that these are the same people they've always known, it will be impossible to hate them" Not saying that applies to everyone, of course, but broadly it appears to be true.
The other day I saw an old man and old woman walking down the street in front of my house (I was working under one of my cars). The woman says something like "I like Jimmy, but how is Johnny supposed to live a happy life with him?" and the old man stopped her for a second and said "Its legal for them to get married now, Edith. Besides, if it makes Johnny happy then who am I to complain"
This is what modern liberals and modern democrats cannot seem to wrap their heads around. Every issue is a societal one, every solution is a moral or spirtual one. It all comes off a heady and a bit in the clouds. The messaging doesn't seem to come down to the individual level anymore, how will this affect or benefit your life on the day to day. Make it real and personal for people.
Bernie isn't changing any minds with this, but if he gets a couple people to stop and think "Its communism alright! But they might not be evil, and it looks like their heart is in the right place..." then its a step in the right direction. Its not all changing overnight.