Was this invocation inappropriate? Need help to write letter....?

I recently attended a collectors convention. At the end-of-convention banquet, there was an invocation given before the start of the meal. It was over-the-top christian, no ifs, ands, or buts about it. Only christian references. We are a diverse group, except that we all have a pion for our shared collections. I think this was grossly inappropriate and would like to write a letter to the convention organizers requesting that they either drop the invocation or provide one that is more religiously neutral. I would appreciate your thoughts - was it inappropriate given the diverse crowd? Any thoughts on how to phrase the letter to the organizers? I don't want to sound mean or disrespectful, just want to get my point across.