I have personally worked for a Canadian Member of Parliament. I totally understand what this guy is going through. If he gets two emails a day from this pressure group, he's lucky (note the source that came from - the pressure group).
I would often spend the the ENTIRE morning going through email bombs. I'm talking 200-300 emails or so per day. Much of them were profanity laced, and not directed to my member in particular, but mass mailed from pressure group websites using a form to blast the entire Parliament of Canada. People would often send the same email several times PER DAY. The only tool the IT department allowed me to use was MS Outlook Message Rules (which helped, but not nearly enough).
It was all about repetition and "louder is better". It borderlined on harassment. I genuinely got excited when I got a well thought out, original email that I could respond to. Unfortunately I had less time to deal with their issue because I had to deal with morons thinking anyone above me would care about their repetitive profanity laced email bombs.