See the problem? It's not a matter of the glass not being spilled. It's not a matter of the funny speech being given. What's problematic is when in the timeline of events each specific event occurred. Surely we can agree that either the glass was spilled "during" or "after" or possibly before (meaning both witnesses were incorrect), but we cannot say that it happened both "during" and "after."
In the gospel passages, it is impossible for Matthew/Mark to identify key specific events that took place in the upper room while at the same time Luke identifies those same key events but in a different chronological order. We must accept one account and discard the other in reference to the timeline (not the actual messages themselves). Much like the best man at your co-worker's wedding, several events took place, but it is physically impossible for both accounts to be objectively correct since they directly contradict each other (as the glass could not be spilled both "during" and "after" the speech).