I'm going to push past a family blocking my way
How are you going to pass that person through the door?
I'm going to threaten them to move or I will push them away because this thing is important
You shouldn't push people or threaten them just to get them to move. You can simply ask them politely to move  and they will very likely do so.
Why should I be nice when I can be a cunt (pardon my language)?
Because being nice is always the best way to handle things especially a conflict and it can go a long way.