Yes, I've already acknowledged the ambiguity in the original sentence, and I apologize again to you for any confusion it caused you.
However, please learn that ambiguity in informal speech/writing is substantially different from errors in formal edited speech/writing, and different responses are appropriate.
In the context of formal writing (e.g., an academic or industry paper, book, etc.) we should expect almost all ambiguity to be edited out, and not allow for inferences in either direction; i.e., your complaint would be valid.
However, in casual speech/writing (e.g., SMS, social media comments, non-formal emails, etc.) it is common and not serious to leave IMPLIED components in the conversation. It is certainly acceptable to ask for clarification such as "did you mean to imply that some area was made entirely inaccessible by that event?". But it is inappropriate to accuse someone of being dead wrong by leaving out the implication.
The request for clarification should result in the speaker/writer saying "ya, I did mean to imply XYZ, not PDQ, thx for pointing that out." — mutually and efficiently finding the truth. The accusation, especially continued insistence on the accusation being the one true correct way, is the way to start an argument trying to establish dominance.
It might also be worth noting that your class of people — those familiar with the Baltimore area — should have been MOST able to recognize that "not directly" was the inferred meaning, since you know it's not linking an island to the mainland. That you chose the hostile "j'accuse — you are wrong!" form of discussion rather than the collaborative friendly "btw, you did not mean to imply that the bridge linked to an island" (and continued to insist on the hostile approach) tells us all that this is more about your emotional state and/or approach to human interactions than about the ambiguity itself.
Have a great week