Probably what he means is that most "research scientist" or "research engineer" jobs out there require a PhD. Though there are a fair number at larger labs that only ask for a masters. But:

>I'm not sure what this means--no-one can stop you from doing research anywhere, regardless of your qualifications.

This may be true in CS, but in most physical or biological fields is not fully true. The permits you need for handling certain materials are more difficult to obtain without a PhD, and it's hard to get funded without it as well.