Clarify BRP Attack Vector

Do we assume or not assume that the public keys were exchanged through a secure channel? The following sentence seems to imply the former.

protocols/BRP.md

@@ -22,7 +22,7 @@ Before they can connect, the peers need to know how to contact each other. A str
 
 We assume the adversary can read, modify, delete and insert traffic on all transports at will.
 
-We do not assume that the peers exchanged their public keys over a secure channel. If the adversary intercepted the prior exchange of public keys and replaced them with its own public keys then BRP does not detect or prevent man-in-the-middle attacks.
+Practically we should not assume that the peers exchanged their public keys over a secure channel. If the adversary intercepted the prior exchange of public keys and replaced them with its own public keys then BRP can not detect or prevent man-in-the-middle attacks. (Limitation)
 
 If the adversary knows both peers' public keys but did not replace them during the prior exchange then BRP prevents the adversary from learning the peers' network addresses, unless the adversary can see the addresses by observing the underlying transport.