In a conversation, こ〜 (これ、この人、こいつ and so on) points to something / someone near the speaker. そ〜 points to something / someone near the listeners, and あ〜 points far from both. But こ〜 and そ〜 don't point to the speaker / listeners themselves.

Now, what if you think / murmur to yourself about the listeners in the middle of the conversation? You are now both the speaker and listener. People who once were the listeners are now just a topic of your thought, so you point to them by using こ〜。 For example,

(...こいつら、ちゃんと俺{おれ}の話を聞いているのか?)

When you use こ〜 to point to the listeners, you are pretending to speaking to yourself and it conveys nuances such as anger against the listeners.

In a conversation, こ〜 (これ、この人、こいつ and so on) points to something / someone near the speaker. そ〜 points to something / someone near the listeners, and あ〜 points far from both. But こ〜 and そ〜 don't point to the speaker / listeners themselves.

Now, what if you think / murmur to yourself about the listeners in the middle of the conversation? You are now both the speaker and listener. People who once were the listeners are now just a topic of your thought, so you point to them by using こ〜。 For example,

(...こいつら、ちゃんと俺{おれ}の話を聞いているのか?)

When you use こ〜 to point to the listeners, you are pretending to be speaking to yourself which conveys nuances such as anger against the listeners.