A quick "such to clarify, are you saying / implying ___?" prevents you from lashing out at someone for saying something they're not actually saying.

This isn't such an uncommon mistake, as many of us are wrapped up in our own thoughts and can get more carried away with listening to our inner voice rather than what is actually being said by our conversational partner.

Say for example, you're at work, and you're upset that you just had to deal with a really rude and hostile customer. When talking to your co-worker about it, they make a comment such as "too many people are just not taught how to treat customer service workers", which you take as them defending the customer and their behavior. Before you start lashing out at your co-worker for your assumption that they're trying to defend the actions of this rude customer, double check that that's actually their intention.

Or say you're on shift with a co-worker who usually works shorter shifts than you due to being part time, but today they're staying as long as you to help out after someone called in sick, or a particularly busy day. If they comment "wow, I haven't had a shift this long in a while", before you start chastising them for being a wimp who can't handle long shifts like you, are they actually complaining or saying they can't handle it? Or are they simply voicing an observation about how long they've been there?

Or say your friend comments "I think I might have x disorder", before you start scolding your friend on how allergic you are to self diagnosers, are they actually self diagnosing? Or are they simply voicing a suspicion about themselves that they might be interested in checking out with a doctor?

It's best to avoid because few things in a conversation are more frustrating than a conversational partner suddenly scolding you and lashing out at you over something you weren't even thinking or saying. It's a good way to sour a relationship, as well as our own reputations as someone rational or reasonable.