There are a lot of things going on in this thread, so please bear with me.
Remember, you are the VFR PIC. You are the sole person responsible for the safety of your flight. My job is to ensure you don't engage in spot welding in the skies. My job doesn't alleviate the VFR PIC's job of seeing and avoiding other aircraft, or ensuring proper weather avoidance. As a radar controller, I don't know where the clouds are. I do know, however, if there is any observed radar traffic conflicting with your flight. If I judge that a VFR aircraft will fly dangerously close to another aircraft, and the VFR PIC does not see the other aircraft, I will take appropriate actions to avoid a collision.
And I've said it before, my colleagues on here have said it before. We would rather talk to you and know what you are doing. At least this way, we can effectively ensure your flight won't become an unsafe hazard with the jet screaming along at 5-6 miles a minute.
Why is getting a Bravo clearance so important?
Class Bravo airspace is positive control airspace. Aircraft require clearance for entry into positive control airspace just like they require clearance for entry into Class Alpha airspace (at or above FL180). That's because ATC separation standards apply to all aircraft. There is no possibility of non-participating aircraft. If you aren't cleared into Bravo airspace, remain clear. It's as simple as that.
ATC separation standards for VFR/VFR and VFR/IFR aircraft differ based on weight and wake turbulence (or wake RECAT) categories. As such, it's not as simple as see-and-avoid which is the standard in all other classes of airspace. In addition, flight through congested Class Bravo airspaces requires accurate flight. Aircraft must maintain accurate altitudes, headings, and sometimes speeds to safely transition airspace. Given that my duty priority requires the safe and efficient movement of IFR aircraft prior to VFR aircraft, I will tend to delay vector a VFR aircraft if it becomes operationally advantageous to the other aircraft in the airspace (hint: it usually is operationally advantageous, as the VFR aircraft is almost never at same speed or same pattern as the other aircraft in the airspace).
Transitional flight through the Bravo is different than flying a published VFR corridor. VFR corridors have been established based on regular IFR traffic patterns. Flight through those corridors and adhering to their restrictions will ensure ATC separation from normal IFR flight patterns. That's why the corridors are restricted both in routing and altitudes.
The OP's story
It sounds like you were not given any special navigation instruction (i.e. vectors, cleared to fix, etc.). If that be the case, the responsibility for securing a clearance to transit Class Bravo airspace rests solely with you. Being on flight following does not equal clearance. Assuming ATC cannot accommodate a clearance into the Bravo, the controller will expect you to either turn, climb, or descend to avoid the Bravo airspace boundaries. It also sounds like you transit the airspace frequently, and as such expected the same treatment as before. In any case, the controller was correct: you didn't have a clearance for entry, you don't enter the Bravo.
Without an audio and radar playback of the event, any discussion into the professionalism of the controller would be hypothetical at best and hyperbolic at worst.
A controller's vector (instruction) and pilot concurrence
Workload permitting, controllers may suggest vectors or altitude instructions to VFR aircraft. The VFR PIC receiving radar services has the final say on any instruction a controller gives. ATC may issue vectors and/or altitudes to VFR aircraft with pilot concurrence.
What is pilot concurrence? According to many, pilot concurrence is the read back of any instruction to the VFR aircraft. If you, as the PIC, receive a vector or altitude instruction and you read it back, you are concurring with the controller's suggested instruction. That suggestion then becomes a clearance, which as we've seen from CC responses, must be followed. If you, as the VFR PIC, observe that an ATC instruction will put your flight into a cloud, or unsafe proximity to positive control airspace, you must notify your inability to safely comply with the instruction.
Good pilots usually follow with a plan B:
"Approach, N123 unable heading 120, that would make us IMC. We can give you a 090 or a 150 heading to avoid the cloud."
Notice I didn't mention the hypothetical "but I got vectored into the Bravo!"
What about getting a vector into the Bravo?
I find this situation very rare, for it involves several obvious links in the error chain. First, the controller vectors a VFR aircraft into Bravo airspace, meaning the aircraft had to already be in close proximity to the boundary. Second, the controller forgets about the VFR aircraft, which might be plausible given workload. Third, the pilot does not take action, either verbally via questioning or physically via a climb/descent/turn, to abide by 14CFR91. Finally, the controller does not issue required clearance into the Bravo airspace, potentially costing him or her an operational deviation for the airspace incursion.
At a minimum, if you have accepted a vector, have you began evading maneuvers vertically around the airspace? The vector was not an altitude instruction, and there is nothing stopping the VFR PIC from climbing or descending to avoid the vertical limits of Bravo airspace. In fact, many controllers expect the VFR PIC to initiate such a maneuver. A prime example would be an aircraft cruising at 5,500, vectored southeast toward a Bravo shelf with floor/ceiling altitudes of 4,000/10,000. A descent to 3,500 is out of the question (assuming no clouds of course)?
Henning and the others have it right, ladies and gentlemen. There is nothing wrong with getting clarity, or asking for the "magic words." We are all pulling on the same oar here, if you'll pardon the expression. Controllers want to help out when we can, and if we can provide an operational advantage to a VFR flight, we do so. Sometimes, in the heat of the action, we forget the "magic words." As a pilot, you can help out too.
"N123, fly heading 120 for (insert reasoning here)."
"Heading 120, N123. Verify cleared into the Bravo?"
