Before there is too much more constitutional blathering about the Sandra Bland contact by the clearly out-of-control cop, we need to lay out the law, especially because most television news so-called legal experts do not know what they are talking about regarding the lawfulness of the cop's demands on Bland. Like it or not, the US Supreme Court ruled in 1977 [Mimms] that cops can order people out of their vehicles to control the scene on the most minor of traffic offense stops. In 2001, the Supreme Court dropped the other shoe [Lago Vista] and ruled that a person can be taken into physical custody and jailed [arrested!] for the most minor of traffic offense, a fine-only offense that does not allow jail time as punishment. That does not mean I appreciate the tone and tension elevation unnecessarily caused by this cop, but I am troubled when so-called experts on the law are allowed to spout patently erroneous assertions regarding what is allowed and what is legal. Constitutional law is serious stuff and you should not be eliciting and then publishing views from those who clearly don;t know what they are talking about.
It should be recalled, as chronicled in Federalist 78 and elsewhere, that the Framers intended the federal courts to protect people against out-of-control government. Of course, the recent and evolving history of the Court is that it does quite the opposite - it protects power far more often than liberty in a liberty vs power contest. The Framers notion was that liberty would be the default position in individuals' relationship with their government, but the High Court has turned that founding notion on its head, in essence working a judicial revolution, which reached its nadir, or court, in Bush v. Gore - a judicial coup d'etat.
But be that as it may, and whether the opinions are consistent with the intent of the framers or not, the law clearly is that cops can order traffic detainees out of cars or do other things [put out the cigarette!] to control the scene, and they can jail people for traffic offenses that do not invite jail as a punishment, and supposedly educated people misstating that to an increasingly ignorant and volatile public is grossly irresponsible.
Here, it was later suggested that Bland was arrested for striking the cop. Whether that occurred or not, he told her up front she was under arrest, and he had the constitutional authority to do that, even though his wisdom in pressing matters that far is highly questionable.