Last Visited Shows Dec 20th 2017 but his last activity was on March 10th 

That might be possible if he's been visiting as 'Anonymous' since December 20 2017.  

It would be better to hide entire block with last visit date if user logged in as anonymous, or write "Hidden" instead of date at least.

You could also use 

 to improve the experience because it's going to show the real activity time to admins?

 

 

Actually, the right answer already sent. But, guys... this field should be the little bit smarter. I mean... okay we hide our visiting. But if we post something this post with current date shows in our profile activity with the right date. I think last visit field should change on the content adding action. It looks very strange and unclear without this logic.