Or as it is otherwise known, abide by the same KYC rules as banks.
I'd guess the vague wording is to allow regulators and the judiciary to respond flexibly to changing practices. It might be broad but it isn't poor lawmaking: it does exactly as it intends to. Even using brokerage as an analogy makes sense to respond to a system in which by design almost everyone of significance is a middleman of some kind.
Fundamentally this is what will allow bitcoin to thrive: this is part of the process of becoming legitimised. It isn't what the crypto-libertarians hoped for, but what they hoped for in the beginning was endless deflation, untaxable income and speculative gains. It wasn't good for anyone but them.
This is a step to something better, namely a new financial system in which upstarts are able to enter quickly and on technical merit alone. That is worth a lot, and won't happen without bitcoin entering the regulated mainstream.