100% get one, they are hella cheap now a days. For $50 - 100 USD, the evidence, peace of mind and eliminating ALL he-said-she-said scenarios seems like a no brainer to me. Very small chance but some insurance companies even give a slight discount for you even having one. Anytime anyone else drives your car, you can see how they treated it, what they said, etc etc.
As for it backfiring on you, I mean you don't HAVE to give the footage to anyone unless you want to. All the footage will be on the SD card in the dash cam. You can always edit out footage if you are singing embarrassingly too.
I have the Anker Roav and it works great, but there are many better ones for more money out there too. Some have front and back facing cams. Make sure you get a 'high endurance' SD card.