We detached this subthread from https://news.ycombinator.com/item?id=14912145 and marked it off-topic.

A "healthy dose" of something negative is bit of a sarcastic idiom. More generally a "healthy" dose could be described as one that is not lacking in any way.

See definition 4

https://www.merriam-webster.com/dictionary/healthy

It means a significant amount of racism.

good point. never.