Keep in mind that an enormous amount of business is done through personal relationships. Future job offers, sales, and other opportunities will come from people you have worked with in the past and who respect you. So, focus on that.
Keep the formal resignation letter short. It's perfectly fine to include a few pleasantries (unless you plan to sue them for something in the future.)
Then, if you wish, have some private conversations with management and give them an honest assessment of how they could better achieve their own purposes. Keep the focus on helping them. Take your former bosses out for coffee they next time they visit. Give them insights that they would not other get. Keep up your relationships with your former colleagues as well.
That's the purpose you should keep in mind. It's more than not burning bridges. It's about creating future opportunities for yourself. Create lemonade from today's lemons.
Edit: do this even if they're all evil bastards. You never know what will come of it in the future.