David Trimble, who has just died, has rightly been praised for his courage. History may prove him to have been Unionism’s last statesman. But the well-known people who sincerely eulogised him this week – Tony Blair, Bill Clinton, Jonathan Powell – all helped end his career. There are many good things to be said for the Belfast Agreement, and no one said them better than David, but it achieved at least one big, bad thing: it undermined moderation in Ulster politics.