CRA employees are just trying to do their job. You should respect them for their service and be professional. If you have tax trouble you should also understand two more important things about the CRA:
1. They have the power to inflict a lot of pain and eat up a lot of your time; please handle with care.
2. In my experience the CRA appears to be organized in such a way that negotiation is difficult and requires a lot of patience. An understanding of your options is a must to have any hope of resolving a dispute in your favour.
Take the first step to putting your tax trouble behind you. Even better, stop it before it starts.