We all know someone who does that. We've all run into someone who does that.
Someone who zeroes in on the smallest, most imperceptible flaw. Someone who belabors the most minuscule and obscure point. Someone who makes something of negligible importance the crux of their argument.
People like that don't understand that the trivial isn't important. That's why it's called trivial.
Picking nits, trying to punch holes in something by making a big deal out of an insignificant point doesn't demonstrate highly-developed reasoning. It doesn't demonstrate a keen intellect. It doesn't illustrate your attention to detail.
It makes you look like a petty, insecure little person who's desperate to get others to listen to you in any way you can.