You're the one that claims opinion polls don't matter, yet here you are, citing another opinion poll you think makes your point
Sanders plan doesn't force anyone into Medicare. It provides healthcare coverage for millions of people without it. The individual mandate in the Affordable Care Act forced people to buy into it under threat of financial penalty if they didn't. Where were your cries of tyranny, then? The way insurance works, if the wealthiest individuals can simply opt out of it because they can afford to buy private insurance for themselves and be taken care of, the system would fail. Everyone is required to opt into the system because, just like Obamacare, it wouldn't work without them. People like their doctors, not their insurance policy. Under Sanders proposal, nothing changes at the point of service except the provider. This has overwhelming support within the Democratic party and majority support among Republican voters.