Are they all legal cc videos? I chose a video from "A"'s channel which was a cc video. Later on, I found that the video was not actually a cc video. "A" downloaded the video from "B" 's channel &amp; introduced the video as a cc video. Now on good faith considering it a cc video, I uploaded it from "A" 's channel. Now...if "A" 's video channel is terminated for violation of youtube policy for this illegal practice will it be harmful to me??..
I'm not a copyrights lawyer, but I think you can consider your use of the video just as much a violation as 'A's version. 
When someone claims the rights to YouTube, you will also receive a notice and the video will be deleted.