He has made a large number of questionable comments, including the argument that the solution to human trafficking includes legalizing child prostitution:

27 April 2015 (Human Trafficking Act)

The Senate's Victims of Human Trafficking Act is dangerous in several ways.

When it talks about having the customs agency do more to enforce "intellectual property", I am sure that refers to something bad. Whenever that term is used, something nasty is afoot.

The way to protect children from being forced into prostitution is to legalize prostitution by licensed prostitutes. Customers could be required to check the prostitute's license. If the customer fails to check, that concrete omission would be legitimate grounds for punishment.

Minors should not be denied prostitution licenses in a blanket way, but the state should ask them why they want one and probe their situation, then offer help so they can avoid prostitution.

https://www.stallman.org/archives/2015-mar-jun.html#27_April_2015_(Human_Traffickting_Act)