Could a larger consumer drone "take down" a passenger plane?
If your definition of drone is any remote control aircraft freely available to consumers, then the answer is yes, but highly unlikely.



Its very unlikely, but it is possible. First, I'd like to point out that Radio Controlled Aircraft (RC Aircraft) have been available to consumers since at least the late 1950s. Hobbists build RC aircraft all the time, and when I was a kid I built my own RC aircraft that was much bigger than most commercially available "drones". To focus on drones alone misses a big slice of the pie. RC aircraft are sometimes built as 1/4 scale models of the original aircraft and can weigh 100lbs or more, so imagine a remote control aircraft that is 25% the size of the real aircraft. 

So, the potential has always been there for at least the last half a century for a remote control aircraft to have enough mass to potentially cause a serious collision with a real aircraft. Imagine if a couple of 18lbs geese took down  Flight 1549, what would a 100+lbs quarter scale RC Aircraft do. 

Personally, I've never been too concerned with this because I've flown both RC aircraft and real aircraft. It would be extremely hard for a drone or RC aircraft pilot to target an aircraft and hit it in its most vulnerable locations such as cockpit or engines. 

So, yes, its possible, but I would not lose any sleep over it.