I don't think this is a conspiracy at all. But I could see people having this conversation if they did shoot it down.
Maybe to make the victim's family feel better. To avoid lawsuits. Avoid repercussion if they were wrong. Avoid repercussion if we found later this plane was going to hit a building that would have little loss of life vs passenger count.
There could be rationale there if people made a panicked decision.
In the atmosphere after 9/11, and especially before Iraq, it was unlikely if not unthinkable that there would be "lawsuits" or "repercussions" for the government. The reason Flight 93 ended the way it did was because every American who witnessed or heard about what happened in New York that morning fundamentally understood that a hijacked aircraft was no longer a hostage situation, but rather a weapon of mass murder. Nobody would have questioned the decision, just as virtually nobody questioned the other decisions made by the US government in the initial months after the attack.
