You bring up a good point and that's that alluding to penis length comparison by mentioning a tape measure is not "no uncertain terms". "No uncertain terms" would mean saying, "I resent that implication. Let's compare the length of our penises."

I actually said something like "do you really want to have a penis measuring contest?"

Being somewhat coarser language than I would normally use online, I decided to initially use a euphemism here while suggesting that other language was used.

Exactly, but I was afraid it was too pedantic to just point it out :)

I used slightly coarser language because I was getting quite angry at the sales pitch.

Ah, I was just amused by the thought of someone saying "perhaps you would like to borrow a measuring device maybe, if and when I felt like lending it to you. Maybe".

Presumably to measure the exact dimensions of the afore-questioned manhood. I haven't heard that expression before either. :)