Yeah...if anyone finds a new link, please post it.
Most best man's speeches are mainly about the friendship between best man & groom, yes. Sometimes the best man might not know the bride all that well anyway, so wouldn't know enough to talk about her, and occasionally the Father of the Bride will do a speech which is more about the bride.
I didn't have a problem with the "ridiculous" bit. It was said in a light hearted way and shouldn't actually be taken literally. There's definitely different ways to use the word ridiculous.
Example One: Dismissing a theory
"That's ridiculous. No way that could have happened."
Tone: Dismissive, critical
Example Two: Friendly banter
"You're ridiculous, mate!"
Tone: Light hearted, jovial.
Sherlock's use of it was closer to Example Two than Example One, is what I'm trying to say.