That is 2 tons hitting it in 1/10th of a second. It used to, as has been proved, moved Javelins.
On the other hand there are certainly plenty of instances of aircraft continuing to fly some considerable distance after a crew member has ejected, even using a pure gun seat (e.g. The "Tintagel Hunter" and the Lightning that had to be abandoned off Valley with a gear problem at Valley in ?'79), so perhaps at reasonable air speeds the pitch down is not as pronounced as one would think - best I leave the theory behind that to the likes of JF.
OTOH a gun/rocket seat firing certainly produces a jolt and a lot of noise but doesn't always produce a large pitch down.
MB , and others, had the advantage of expecting it
Well FWIW I wasn't .......
even so the aircraft didn't dramatically didn't pitch down..and in fact it kept going for several miles.