Saying 'no' when you mean 'yes'

Yesterday Luc and I were at the gym using an incline bench for something that we only needed  a flat bench for.  All the flat benches were taken.  The guy next to us using the flat bench decided that since we didn't need an incline and he wanted to change exercises offered to do the ol' switcheroo so that we'd take his flat and he'd take our incline.  Fair enough.

He said, "hey do you guys mind if we switch benches?  I've only got one more set here and would like to use the incline."

"Ok, sure"

We waited 30 seconds then proceeded w/ the switch.  As I hovered over the bench, I noticed that it was slightly glistening [i know it's gross] from this heaping gentleman's last round of lifting heavy things.  It wasn't water.  I believe that the man noticed me notice his bench.

He said, "do you want me to wipe that down real quick?"

I said, "NAAAAAHHHH"  

What I really wanted to say was, 'hey yeah that'd be great' or 'i'll get it,' but instead I just said 'naaaah' and plopped down and went on w/ my workout.  The entire next set I couldn't really focus b/c I kept thinking about how I was laying around in this guy's sweat because I was too stubborn/lazy/embarrassed/annoyed/caught off guard to just...say...yes.