To be assertive when you are right is a good thing . To be assertive when you are not so sure is where it becomes difficult.
I do not mind anybody (and that includes my wife !) to be assertive once in a while if in the end he/she is proved right.
I would even argue that in this instance, it doesn't matter whether ATC are right or wrong about whether an aircraft can complete an approach from a particular position. They are moving the whole operation in the direction of increased safety.
I'm not sure why pilots have a problem with this - when ATC tell you "turn left heading 200 degrees" or "descend altitude 4000 feet" or even "GO AROUND, I SAY AGAIN, GO AROUND, follow standard missed approach procedure" do you immediately prepare a counter-argument or start frothing at the mouth with the indignity of it all?
I am all for assertive ATC, I mean it's supposed to be a CONTROLLED environment isn't it? It's good to know that there are still some ATC'ers left who will try and stop a dangerous situation developing by timely intervention, rather than waiting for the "whoop-whoop" (or the crash
).
You don't have to look back far in aviation history to see what happens when you combine pilots having a bad day with wishy-washy controlling. I don't know when my next bad day will be; I hope it never comes but if it does I'd like ATC to speak up with their concerns sooner rather than later...