The rationale is very simple, the moment you proposed the game be all vanilla there were only three options:

1) You were vanilla
2) You are roled and deliberately put forth a scenario you know is impossible for serious consideration
3) You are scum and role fishing

Note that all three of these options make you worth less to the town than an unclaimed. If 1, well a vanilla can be useful to the town, the games not all about roles, but one of their greatest uses to the town is as NK bait. If 2, who will trust anything you give us regarding your role after implying we had none? You may be useful as a vig, but even as a bulletproof, you're compromised because no one will try to attack you thinking you're vanilla. That's why you're high on my list for lynch today.

As to why I claimed role, I was hesitant to RC, however the conversation began continuing, everyone who might reply supporting the idea would be signaling they were vanilla as well. This could easily have cascaded, and been disastrous. Someone had to claim a role before anyone else claimed vanilla, and there were 3 reasons I had to do it.

1) I am roled, and know the game is not low on roles, let alone absent them
2) I knew of the problem, I could not be sure anyone else did, and I could hardly risk saying "Could some role please step up and disprove this?"
3) Realistically, I am already a very high priority target, barring an outright claim of cop or doc by someone I can't imagine anyone being a high priority target then me come the night, so what difference does it make? The scummers will either strike or not, concerned over what protections I may have, and I will either have those protections or not. Same formula as always.

Therefore it made sense for it to be me, since I was roled, was aware of the problem, and already a high-prob target.

You have not adequately explained away why you made the move, which is blatantly anti-town. Nor explained your 'maybe' responses.