I need to let it out

It is the most reasonable sounding idea in the whole subject. Pressure builds, so release it. Shout in the car, hit something, get it out of your system.

The trouble is that it does not behave like pressure. What you practise, you get better at, and what you get better at happens more easily next time. People who discharge their anger physically while thinking about the person who angered them do not come out calmer at the other end.

There is a real distinction to keep here. Exercise is good for you and lowers your baseline, which is genuinely useful. Exercising while running the argument in your head is a different activity with a different result.