Allowing one side to advertise doesn't mean the other side doesn't get to "put their position forward."

If, as you say, not advertising on twitter doesn't mean you don't get to put your position forward then nothing of value is being lost by the twitter policy change.

I'm saying that allowing A to advertise on twitter doesn't prevent B from advertising on twitter.

If one side has a financial incentive to push bad faith arguments, whereas the other side has no financial incentive or resources and is just interested in science for the sake of science, then by supporting having the debate via twitter ads you've created a system that locks out one side.