It’s hard to imagine that a spaceplane would have a larger environmental impact than a rocket. Since we are going to continue sending things to space, a spaceplane would have a positive impact on climate change.
It’s still launched by a rocket. The plane part is only for landing. Whether this will actually work or be more efficient than ablative re entry remains to be seen.
Cheaper satellites are a good thing environmentally though, as it will be how any emission controls will be monitored.