CMMI vs XP

Most people think CMMI is on the other direction of XP, including PQA of my current project. According to my understanding, there is no principle contradiction. The same words was expressed by our QA manager a year ago, but I only understand it recently. XP just did some practice in a special way, while CMMI does not specify the way you should implement a practice.
CMMI is "bad" because the book is of too many pages to most people and XP fans are reluctant to read it. CMMI try to measure determinately, but the measurement is based on assessment of people, which is often inaccurate. I don't know how far it could go.