As someone with Italian heritage, I noticed a long time ago that when I feel I have something important to say, my hands like to try and do my talking for me.
As much as this fact can amuse me from time to time, it generally doesn't come up mid-conversation, as what I'm talking about apparently carries enough weight that my hand motions seem like a minor detail.
And based on his response to President Trump's comments about his own hand gestures, it seems that Beto O' Rourke is hoping this will also ring true for him.