I've just finished sending letters and signing a petition to say that Elizabeth May should be a participant in any national leaders' pre-election debates. I hope you'll go to the Green Party's site to make your voice heard too: http://www.demanddemocraticdebates.ca/?
It's good to direct a letter to a specific person or agency, not to just send the same one to all. And, in this situation, you might want to copy your letter to Elizabeth's assistant, Nyssa McLeod (email@example.com) so they know that people are writing.
Here's my letter to Jennifer McGuire, General Manager and Chief of News CBC:
Dear Ms. McGuire,
I believe absolutely that Elizabeth May should be part of any televised (or radio) national leaders' election debates. There should be no doubt that May is the leader of a national party. From the votes received by the Green Party in the 2008 election, the Green Party is a wanted voice for Canada. It is the fault of our electoral system that the opinions of a million people are missing from government; it is not the fault of the Green Party. An important Canadian asset - the CBC - with its excellent environment programs, and non-sound-bite news, is the last station that should be interfering with democracy and with a real possibility for having a leader who understands the critical environment issues we face. I am ashamed of you. You should be ashamed of yourself.
Given that the leaders of the four other national (or Quebec) parties do not object to May being on deck with them, what excuse is CBC giving for her exclusion? I look forward to seeing you personally interviewed on CBC on this; I suggest by by George Stroumboulopoulos or Peter Mansbridge.