it's government propose the motion, which is the formally proposed proposition. and
opposition side are against their proposition, because this motion will do more harm than good.

actually, everything has two sides, and from one side, you are standing on a particular stance and voice for a range of citizen for a part of stakeholder.
and the opposite house are standing on another stance and voice for the rest.
both sides must have some justified reason to stand on the stance, but must have some problem can be attack.

what the debater to do is not convince the opposite debater, but make the audience understand the motion, a complicated issue better, more completely and deeply. to broaden their view.