This is not true. This is only true when you are TOTALLY ignorant of what is happening; if you really have NO IDEA whatsoever of the things that are happening. Ignorance is bliss only when it is true.
When you have an inkling that there might be something wrong, ignorance is not bliss. It will always come knocking on the side of your head, on the peripherals of your mind. Yeah, you may push it away but it will come back to haunt you. How long can you pretend to be ignorant? How long before it starts bogging you down?
How can you say ignorance is bliss if you're not really ignorant of what is happening?