They don't need backdoors for targeted spying - they can plant hardware bugs or hidden cameras to watch the target type in messages and passwords. So the only reason they'd want them is to use them on scales where targeted spying is infeasible.
How will people know it's not done in bulk? The only thing that the public sees is the client binary. A client binary with a backdoor looks the same whether the backdoor is used one time in a million or thousand times, or a million times. The companies might publish reports on how often they got asked to access the backdoor but they might be compelled to lie or even be hacked and not notice it, or they might even use the backdoor themselves to extract more revenue.
When surveillance is being rolled out, it's always just about a few single cases here and there. And then gradually, silently, the number increases.
The pretext of the meeting (and others like it) notwithstanding, it's not unfair to say that strong encryption renders communication to a state closer to the pre-digital era in terms of the amount of work required to perform individual surveillance. I think that was the point deogeo was making, and it seems like a sound one to me.
This is the line the Australian anti-encryption bill that past last year was trying to walk with its "no systemic backdoors" clause.
The idea/claim was that the bill only allowed targeted spying, and systemic/bulk spying, so it's okay. But that's really only only a small part of it.