A B717 Captain reported encountering wake turbulence in descent from a preceding MD-11.

Narrative

During takeoff roll I heard another aircraft Pilot ask the Local Controller when they can expect to take-off. After departure we were assigned direct ZZZ and a climb to cruise altitude of FL270. The Departure Controller advised us to maintain 13;000. He issued us traffic at our 4 o'clock position; an MD-11 climbing. He then issued us a speed restriction of 280 KTS. We ended up flying direct to ZZZ and our filed route as the MD-11 passed us. We were step climbed in altitude increments of 2;000 feet. 13;15;19 and eventually leveled at FL210. When we were issued a climb to our filed altitude we declined. We actually had the MD-11 in sight most of the cruise portion of flight. We watched his descent profile and planned ours to avoid his wake turbulence. We watched his descent point and started our descent well past his. As we began our descent we experienced an upset from wake turbulence that disconnected the auto pilot and caused an altitude deviation of almost 300 feet. Later the Flight Attendant reported that the upset was quite radical in the cabin and caused spilled coffee and passenger apprehension. The Controller demanded that we begin our descent [which would] create another encounter. I told him of our upset and wake encounter and refused his command until we could ensure a safe descent. While our descent required above normal altitude planning to avoid another wake encounter; we also had to slow and s-turn on final to maintain spacing behind the MD-11. Our flight time was as filed but our fuel burn was 400 lbs over filed. Captain took control and maintained control of aircraft. Because we file one airspeed and fly another; the people who we share the sky with sometimes get tired of following us around at these reduced speeds. I do know of several occasions where pilots flying lower than filed airspeed have caused a Controller to have a near loss of separation. Eventually they will retaliate as their career becomes threatened with these situations. Meet with ATC to discuss it.