Is being passed by them close enough? Don't bother replying if you can't understand the question.
The answer that prompted your agressive response was in fact correct in so far as what it said.
No, being passed by them is not close enough. You need to pass the designated DRS detection zone line within 1 second of the car you are attacking.
If you are successful in doing this it will light up in the DRS activation zone and be useable.
If you are racing cleverly you will know exactly where both these zones are to allow you to both attack with DRS and defend from DRS attack.
For example in Canada (a double DRS zone) the detection point is exiting the hairpin at the "top of the circuit" (turn 10).
So in attack mode you would do all you can to cross this within 1 sec of the prey and then you have 2 DRS zones in which to attack around turn 12 (on the 1st straught) and soon after turn 14. So most of the run down the island.
In defence you would fight (including all your KERs and fuel mix 3) to evade a 1 sec proximity there or most prob will be smoked.
I defence there I have deliberately allowed the attacking car to slip under me B4 the detaction line and thus grant me the DRS for the 2 zones. This was successful as I retook a position I would have otherwise lost for sure.
Another example is that in Hungary a good exit from turn 13 and entry into 14 (final turn)will almost always evade a 1 sec gap to pursuing car.
I hope my answer doesn't in any way offend you.