I know that—I have pepper spray for self defense for that very reason, along with other weapons.
The issue is that you have to feel reasonably threatened still. For a gun, the bar is serious harm, and for pepper spray it can be a much milder threat such as approaching or violent words.
I just don’t see how “hello” is threatening before a verbal order to leave the property. That’s why I think the video is important—her attitude and stance will make a huge difference in how justified the response was.
Looking up his address and going there could be premeditation for harassment or harm depending on how the series of events at the door transpired. It doesn’t matter if he is an alpha male or if she is in a wheelchair, it is reasonable to think that a stranger who has come to your home to confront you over internet posts may mean you harm.
That said, I don’t think he was justified in deploying pepper spray without at least verbally ordering her to leave the property. If he did that and she stayed though…then there isn’t going to be much legal defense available to her in many states.