I need further explanation on airliner tipping due to weight and how planes are on-loaded/offloaded.

I’ve always explained to people that you can’t board back to front on a plane because it could tip the plane back. But as we offloaded a plane the other day, I realized if I were right, the plane should be tipping back during off loading since it’s offloaded front to back.

Can someone provide more explanation on this?