So, this happened.

U.S. government hackers at the National Security Agency are likely targeting Russian government-linked hacking teams to see once and for all if they're responsible for the massive breach at the Democratic National Committee, according to three former senior intelligence officials. It's a job that the current head of the NSA's elite hacking unit said they've been called on to do many times before.
Robert Joyce, chief of the NSA's shadowy Tailored Access Operations, declined to comment on the DNC hack specifically, but said in general that the NSA has technical capabilities and legal authorities that allow the agency to "hack back" suspected hacking groups, infiltrating their systems to gather intelligence about their operations in the wake of a cyber attack.

Hillary says we "know" Russia hacked the DNC, and that's all you need to know.
She hasn't shared this proof with intelligence agencies yet.

This isn't the first nation we've launched a cyberwar against.

The Obama administration has determined that it must retaliate against China for the theft of the personal information of more than 20 million Americans from the databases of the Office of Personnel Management, but it is still struggling to decide what it can do without prompting an escalating cyberconflict.
The decision came after the administration concluded that the hacking attack was so vast in scope and ambition that the usual practices for dealing with traditional espionage cases did not apply.

China Daily writes that the United States risks setting a “dangerous precedent”.
Xinhua reports that the United States is “building momentum for a cyberwar.”

The Obama Administration hasn't bothered to offer proof that the Chinese government was behind the hacking.
Nor has the Obama Administration offered proof that the Russian government was behind the recent hack of the Pentagon’s unclassified email system, but that hasn't stopped them from suggesting it.

The email system was compromised late last month and brought down, in what officials say was a spear-phishing attack, getting email users on the system to click on harmful links. One US official, speaking anonymously, said it seemed “fairly sophisticated,” concluding it may well have “come from a state actor such as Russia.”

The Russian government may have been behind the hack. China's government too.
Or not.
But if you are going to declare any sort of war against a foreign government, even a cyberwar, then you need to justify it. You can't just do it. There needs to be some sort of public debate.
Let's not forget innocent civilian casualties, which happens in all wars, whether it is wars on terror or drugs or other things.
What's more, the laws being passed to legalize this war are very authoritarian and a danger to civil rights.

Back in April, the DHS said that 2% of hacks rise to the level of "prompting a national response". Considering that there are hundreds, if not thousands of attempted hacks every day, that number is alarming.

Pre-emptive cyberattacks is a dangerous rabbit hole to go down. There is no telling where it might stop.
While a cyberwar would most likely be nothing more than an inconvenience for the average American (no one has ever been hurt in a cyberwar, while cows killed 22 people last year), it could have devastating economic effects.

We've already "weaponized finance" in this war.
The legality of a cyberwar could be nightmarish. The lack of transparency remains the same.

Back in early 2013, the Obama Administration declared that the president had the power “to order a preemptive strike if the United States detects (allegedly) credible evidence of a major digital attack looming from abroad.”
The US Cyber Command (USCYBERCOM), based at Fort Meade, is our cyber hit squad. China has their own cyber army.