segwit requires miner consensus, if not, it has huge potential to split the chain.
if 51% of miners agree that its an "anyone can spend tx" then anyone everyone will attempt to spend it.
It doesn't require miner consensus at all, a simple majority would be enough. And there's no huge potential to split the chain, this 'anyone can spend' story spread by BU propagandists has been thoroughly debunked already:
https://seebitcoin.com/2017/02/segwit-facts-not-anyone-can-spend-so-stop-saying-they-can/miners could mine a block that breaks these rules and old nodes would still recognise it as valid.
imagine a simple majority 55% of miners are segwit
the 45% other miners are not.
anyone can spend TX will be spent every time.
45% of the miners see this as valid, the include the TX
55% understand segwit TX and see it as invalid
the chain splits....
the truth is in bitcoin a "simple majority would be enough" applies to anything and everything.
but in the end its all up to economic majority...