Do they Stack?

Case in point: 2 prime sentinels?

What about 2 War on Humanity?

It seems like they would, but we had a guy come in and say otherwise...

If the answer is "no, they do not stack" please explain why this is so.

The effects will accumulate. The most common use of this would probably be 'The New Brotherhood'. Having 4 of them on the field does add up.

Cool.

I figured as much... just didn't want to be cheating when i did so.