I see a problem with AOPA's writeup:
The IMC rating is one of the significant factors contributing to the UK’s high GA safety rate, which is far better than the rest of Europe - France has some 90 fatalities a year, Germany about 80, the UK 20 to 25.
I know they're asking you to tell this to a politician (a professional liar with no regard for or understanding of facts), but from a personal perspective, I would never put my signature to a statement as fallacious, tendentious and unsubstantiated as the above. I am sure the educated users of this forum can immediately see the many blatant problems with it.
Without wishing to speculate as to the possible origin of that statement, and obviously assuming that it was not done in bad faith, I would suggest that AOPA might wish to amend their advice to their members.
Similarly:
There is no credible suggestion that it is unsafe, and there is a mountain of evidence that it makes better pilots and has saved many lives.
What they are saying here, in as biased a way as could be managed is: there are no scientific studies that we are aware of which assess the impact on safety (or lack thereof) of the IMC rating. Even if there was such a study (which would be very costly), it is by no means certain that it would yield any meaningful conclusions.
To put an absurd example which follows their line of reasoning, one could say that the safety impact of the IMCR is as beneficial as employing undertrained ATCOs unable to express themselves in proper English. After all, AOPA's fatality figures for the UK are comparable to those for Spain (median of 24 deaths/yr for the last 18 years. Mean somewhat higher courtesy of Spanair, data from CIAIAC bulletins). Not to mention Andorra's perfect air safety record
Now in my opinion, and I have no axe to grind and don't care about AOPA or the IMCR either way, they are focusing it the wrong way by trying to sell it as a safety issue (something which they cannot factually substantiate) when at the end of the day the only provable benefits are economic.
To take Mike Cross' example, I don't think anybody has ever suggested that doing what a mountain qualification allows you to is an exercise in safety--it's quite the opposite IMO, but without it you couldn't take rich people right into the heart of the Alps and Pyrenees for a day of skiing and then back to their homes elsewhere in the continent, neither would the concerned areas benefit from the presence of people with considerable disposable income (private mountain pilots) throughout the year.
So there you go. I just wanted to point out that whatever the results of their lobbying attempt, if that's what it is, they are doing their credibility no favours with poorly conceived statements as the above, any good points notwithstanding.