Trying to kill Bernie Sanders with kindness?

Francis Wilkinson for Bloomberg says:

Senator Bernie Sanders is a decent human being and a passionate politician. He is also a grave threat to the Democratic Party. Because the Democratic Party is currently the only major U.S. party devoted to moderation and rational empiricism, Sanders’s robust campaign for president is consequently a threat to the U.S. as well.

Classic attempt to kill Sanders with kindness.

If you go in too hard on someone you oppose, you may end up with egg on your own face. The last resort: a civil blow. Tell your opponent he’s a nice sorta guy, then when your critque lands it REALLY lands.

The problem is even this doesn’t always pull off.

See for example when Alistair Campbell, among many others, tried to kill Jeremy Corbyn with kindness:

Corbyn’s a “nice guy” but Labour are finished if he wins.

And then look what happened…