There isn't enough evidence of long term immunity to make herd immunity a sensible strategy. It's smeared by the media b/c it's way less preferable than the alternative of containing it like nearly every developed country in the world.
“This strategy would kill over half a million Americans” isn’t even really a smear, it’s an accurate description of why the herd immunity strategy is bad.
They said the same about tens of thousands dying; we’re now at 141k dead Americans. If you want to dismiss it as “fear mongering” that’s your prerogative, just don’t be surprised that most people find this unconvincing.