The Restaurant was a victim here, not part of the problem.
They were overwhelmed by an unruly flash mob, and did their best to tell them to leave. They physically protected Ted Cruz and his wife by locking the door behind them, and blocking the “protestors” who were trying to follow them out.
Here is some video:
And how exactly did they know he was there? Someone (aka: employee or staff) sent out the alert. So boycott the business anyway. Let the bum who was smirking learn his/her lesson.
Most likely Cruz had made a reservation. I suspect that it was restaurant staff that alerted the protestors ahead of him getting there. Maybe not the restaurant but at least some of the staff is complicit.