The sole question here is whether OP "appeared to be intoxicated" not whether he was intoxicated. That is why the blather about needing blood alcohol measurement devices, determining whether OP was a danger and so on are just that: blather.
More importantly, if one goes back and read the Rule, it is self-evident that no one staff member makes the decision and that the final call is made by the PIC who is required under the Rule to file a written report.
What happened here is likely the routine. OP "appeared intoxicated" to staff. OP reported to PIC. Confab ensues and OP is told he won't be served on the flight. Option to offload.
Never worth speculating about additional facts, but the entire OP is odd in that it describes in detail various social interactions, none of which are particularly relevant. Indeed, if all OP had to drink over the entire journey from STL were the two beers yet he "appeared intoxicated" this was handled correctly. In any event, if he was not intoxicated, the Rule is written to come down on the side of not serving.