First of all, what happens with other channels has no bearing on your own channel's situation or how YouTube treats your channel. That's like saying: "But Mr. X Robbed the bank and got away with it; why can't I do that too?
The other channels simply may not have been caught yet, or they may have been caught and their videos claimed under Content ID; which means that all of the ad revenue those videos make goes to the copyright owner, not the channel owner. They also may have taken the proper path and obtained the necessary licensing. Let me give you a direct quote from YouTube's Terms Of Service.
"7.7 You agree that Content you submit to the Service will not contain any third party copyright material, or material that is subject to other third party proprietary rights (including rights of privacy or rights of publicity), unless you have a formal licence or permission from the rightful owner, or are otherwise legally entitled, to post the material in question and to grant YouTube the licence referred to in paragraph 8.1 below.
then how can I make parodies about talk shows or something????
Contact the copyright owners of the content you wish to use, and obtain all of the following:
1. Copyright clearance and worldwide rebroadcast rights.
2. As you are planning to use broadcast news clips and talk show segments, you'll need to clear publicity rights. This means you will need to have the stars, guests and anchors for each segment sign a Model Release.
3. If you already have a monetized channel, or are planning to have monetization applied to these videos you are planning, you must also get commercial use rights, or the right to make money from your video productions.
This usually costs money to do.