While the Russians did not hack actual voting totals, there is ample evidence that they participated in a campaign of misinformation that benefited the Trump campaign. While we may never know definitively if this gave Trump the election, the mere fact that they meddled in our election process is an assault on our democratic process. 
It was wrong of the Obama administration to not inform the public of this before the election, but worse for the republicans to deny it happened. That's putting partisanship above national security and democracy.