"Well, they are quite correct."
Yes but only for a very limited value of correct.
They are not correct in assuming that criminals will only use legal communication methods if those are back-doored. I've said this numerous times here: you do not stop people intent on breaking the law simply be providing them with more laws to break. Non-backdoored communication exists; they'll use it even if it;s illegal.
They are also incorrect in overlooking the fact that for the rest of us every-day use of the net as a trading medium requires secure communication. I've said this before but obviously you need to check it for yourself: go and look at the T&Cs of more or less anything you're signed up to that deals with money but especially banking. You'll find you are contractually bound to keep things like log-in credentials to yourself. How do you do that if those creds are being passed over the net insecurely? Which, to cut off your likely reply....
They are also incorrect if they think that only they would be able to use the back doors. A back door in encryption is a deliberate breakage. If it exists somebody who shouldn't is going to use it so although you may think you're going to be given secure but back-doored encryption to meet your legal obligations on those cred you're sorely mistaken.
The winners in all this are going to be criminals and any snooper who gets themselves on the back-door snooping list (and in previous rounds of investigative powers legislation that list has extended to unbelievably low levels in your local bureaucracy). The losers are going to be the general public and only the most dense of petty criminals. But mostly the general public.
So, yes, they're correct as regards the densest of petty criminals. Wrong everywhere else. And BTW I spent almost half my life working in criminal investigation so I'm not likely to be against anything genuinely useful.