It's all about timing. FD can't prevent target or destruction effects until after resolving. ECON targets before resolving, so FD can't stop it if they're in the same chain. However, chaining FD to cards like SRH can prevent their destruction effects since they don't activate until resolving.
it does not negate targeting effects, only prevents them. If opponent chains econ to this card, or if you chain this card to opponent's econ, effect still goes through because it does not negate targeting.