Then Parliament has the right to hold a vote of no confidence next week, and get a government it does have confidence in. Or force a general election. Or they can seize control of the Parliamentary agenda and try and legislate their way out of this.
The obvious way being to vote for May's withdrawal agreement, which nobody likes but is a way of leaving with a deal - if a majority really do prioritise having a deal over anything else.
I agree, this removes time from the opposition to do stuff. But backbenchers have already proved that they can work with the Speaker to change that, if they really want.
So yes, while I agree that this doesn't look all that good, cries of "constitutional outrage" are ludicrous. The government has done something it has a perfect right to do. And having a Queen's Speech for a new PM and new government, which has announced new policies is equally not outrageous.
I think the big problem is that the opposition to no-deal are split (which Johnson's agressive tactics may unite against him) - so up to now it's been impossible to get enough people to agree on any solution. That simply cannot go on. He has made it slightly harder for his opponents to organise, but on the other hand limited their options to keep just waiting and seeing. I suspect to force a show-down, because he thinks that the only chance to get any change out of Brussels is to show that he can command Parliament. If they'll block deal whatever, then the EU can just wait until that happens, and the whole fucking cycle starts up again.