Ideally you want to establish an agreeable foundation so you can proceed to your argument and make your case, and then receive counterargument. When people reject your foundation they won't even engage your argument. They'll dismiss it and it won't get off the ground.
This isn't the debate section though. We don't have to follow rules like that or do the ideal thing. It's much looser and let-fly. Whatever amuses us. Yeahhhhh.