They simply deny it. Where i say there is no deceleration, they say there is deceleration. Where i say the plane does not breakup, they say it does breakup.
I've even had someone tell me that the plane would go inside the building in-between the steel cladding. ie all the plane managed to break up and enter via the foot wide gaps between the steel gladding, break the glass and enter. Other arguments include all the plane disintegrated on impact and was not actually going inside, it just vanished as it hit the building and only looks like its going inside.
We can clearly see from every single air plane impact video that has ever been released of the 2nd impact that the plane enters the building, not showing any decelerations, in some cases the planes tail is still completely in tact and a per frame analysis has been done showing that when the front part of the plane was inside the building, the tail was still in the same place as it would be even if the building was not there. Therefore the plane shows no visible signs of impacting anything, as no deformation of plane structure and no deceleration.