Earlier quoted context omitted.
Blocking your videos and holding them hostage until you agree to a new contract would be abuse, yes.
Wait, are you suggesting that it should be forced to continue to distribute your videos for free (to you) even if you don't agree to their terms of service?
Blender already had an account and videos hosted on Youtube. Blender did not change their videos. YouTube changed their rules - and is holding Blender's videos hostage until they accept NEW terms.
These aren't terms already part of Blender's contract - which is why Youtube is literally trying to force Blender to sign a new contract and refuses to execute their original ToS.