Consider this passage from Introduction to Metaphilosophy regarding phenomenology.

This is particularly so, the phenomenologist might continue, when the structures of the experienced objects are what is at stake, rather than the finer details of ’what it is like’ subjectively. In fact, if we didn’t all experience things in roughly the same ways we would be in trouble. If other people didn’t strike all of us - or very nearly all of us - as fundamentally different from trees or lampposts, then our societies would surely collapse. On some fundamental level, we must experience things in the same way. That there are some marginal cases where our experiences differ does not detract from the value of phenomenology in all those cases where we experience things in the same way. (81)

What is the argument given? I.e. what is the conclusion and what are the premises? Is the argument valid and is it sound?

Here is my own reconstruction.

If we didn't experience the world in roughly the same way (i.e. people as people not lampposts), then we would be in trouble (i.e. societies would collapse).
Societies haven't collapsed due to fundamental differences in experience.
Therefore, in some fundamental way, we must experience the world in the way.

The last claim about the value of phenomenology strikes me as a tacked-on comment as opposed to a component of the argument. Additionally, (2) is asserted in the passage without a conclusion indicator word so it is hard to determine if it is a premise or conclusion. However, if it is a premise the conclusion would be that societies haven't collapsed due to differences in experience which would be an odd conclusion given the passage. So, this I think is a charitable reconstruction.

Incidentally, societies have collapsed but the question is whether they did so because of differences in experience between peoples. So, (2) might be true but we would need to see more evidence one way or the other.