why are you trying to assign a value into your case when ?
"Base Facts"."Revenue" = 0
This doesn't make any sense: you can return 0 or "Base Facts"."Revenue" or what you want, but you can't try to assign a value in that way .... (and if you look at your ELSE you don't assign anything, you just return a value, so do the same in the WHEN .... THEN)
case when "Sales Rep"."Sales Rep Name" in ('Michele Lombardo') then 0 else "Base Facts"."Revenue" end
Lesson learnt: never try to tell somebody why he has an error in a piece of code, just give him the right code ...