Bitcoins operate off central Banks meaning the government can not control its supply or influence its value like they do with fiat currencies. This threatens their ability to manage national income. Also since Bitcoin can be pseudonymous, the government worries that people may use it to evade taxes, launder money,Or finance illegal activities.
Why are some embracing it while others seek to regulate or restrict Bitcoin??
The government will continue to fight Bitcoin because Bitcoin is not under their control either by pressure or whatsoever it can't be manipulated,since Bitcoin is decentralized, the government can't force tax payment from its transactions. The anonymity of Bitcoin makes it easier for the users,since their transactions payment and identity can't be revealed publicly, therefore money laundering and other criminal activities can't be detected and it's volatile nature which makes it difficult to government to use as a stable coin.