That's why it's good to meet them and handle them first if you possibly can, so you can get an idea how it might go. Most are pretty tame, and some that aren't at first will tame down after they have a chance to settle in and get used to you, but there are the odd ones that just seem to have aggressive personalities no matter what you do. Fortunately, those are fairly rare -- bearded dragons are known for being pretty mellow as a species in general.
I once read a book where the author speculated that in the wild, when they encounter an animal that's bigger than they are, their first reaction is to freeze and hope they won't be seen, and then if that doesn't get the larger animal to go away and leave them alone, the next thing they'll try is to puff up and flare their beard and make themselves look as big and scary as possible, and if that doesn't work, as a very last resort they'll physically fight -- bite and scratch, etc.
That sometimes translates to holding very still when a human picks them up, and that gives them time to realize: "Hmm... this big animal that just picked me up is not hurting me, and besides that, it feeds me treats once in a while (hand feeding is a good way to bribe them into trusting you), and not only that, it's WARM, so I might as well just snuggle up, relax, and enjoy it." Possible explanation for their tendency to be naturally tame in the presence of a large mammal.
So you've got a pretty good chance of finding a new family member that will at least tolerate your company and maybe even enjoy it