People forget that Youtube is a _business_. The reason they maintain all of those servers and network machinery is to serve ads, otherwise why would they provide that service for free?
Once you download a video, you don't need their service anymore to watch it again. But they want you to remain dependent on them.
No. But they shouldn't harm environment. If business is harmful then should be illegal.
Well that's a pretty simplistic view.
That doesn't mean there isn't some truth to it. ;)
How is it possible to legislate electricity caps on google, according to some imagined threshold of "harm to environment"? Sounds like the number of lawyers involved would be the real harm in this scenario.
Company will have to justify what is their business need for particular use of electricity.