Harmful
Over the years there have been a lot of opinionated harmful pages, and to be honest I've become a fan. Naturally it is much easier to approach things in an inverted way. Rather than approaching things from the stance "what is the correct way", approach them from "what should I not do?" This yields higher quality results as it is inane to expect someone without proper understanding of impractical/harmful implementations to understand the meaning of why an implementation can be good, and furthermore why/if/when a trade off should be made.