Defenders by and large aren’t getting a running start at you. There’s just no room on the field for that kind of high speed travel. If a gentle but firm bump is causing issues, your robot might have some underlying problems you need to address.
My team was targeted by a defensive bot in about half of our 20 matches this past weekend and not once did defense break our robot. Poor wiring on the other hand caused us to sit dead on the field twice (in our 4th & 5th qual match) until we found the problem (thanks to an FTA).
If you think this is bad, you shoulda saw when there were no bumpers. Ah the glory days.