Malwarebytes sums up my opinion on Monero and Coinhive pretty well:

https://blog.malwarebytes.com/security-world/2017/10/why-is-malwarebytes-blocking-coinhive/

It's one thing to let users opt in to mine to support a site owner, but when you slip it in without the user's consent, that's where problems lie.  Too many site admins take the latter approach.  Block Coinhive on site.