Mammoth Tank

And while I don't think there's a right answer to this, I would add that if you click on a space with infantry, the Mammoth Tank should move to that space rather than targeting the infantry.

Neither solution is perfect, but the situations where you would prefer to run infantry over rather than shoot at them are greater. Since the Mammoth Tank isn't good at killing infantry anyway, which one it targets is less important, and with the rare exception of where a move might be bad (holding a missile or chokepoint) there are a lot more where not moving is worse. For example, you can't move onto a missile if it is blocked by infantry.