Should I defer jQuery?

Google wants you to defer all scripts, so the short answer is yes.

However, this can cause some functionality on your site to stop working, so it’s important to check all of your major pages/page templates after making this change, to ensure everything loads and we aren’t seeing related console errors.

If you run into problems, regularly install new plugins to your site, or just don’t want to worry about this, it’s possible to defer all other scripts and leave this one render-blocking. This greatly decreases chances of conflicts, but PSI will continue complaining. 😉