I heard about the comment, but I never actually read/heard what was said. My assumption was that the comment was not made against the entire group, and unsurprisingly, I was correct. While it was not a smart thing to say regardless (smack talk your opponent, not the people you want to vote for you), the remark did specifically state "half of Trump's supporters".
I find that this is an interesting problem that we have as humans, and it has been mirrored in many different aspects of media. I tend to watch a bit of game-oriented content on YouTube, and you won't believe how often I have to hear people toss out the obvious caveat of "this doesn't include all of you", because people
often think it does. It's strange that people can hear a negative remark about a part of a group that they're associated with, and get riled up regardless of whether or not the remark was even made
toward them. Thinking about it just now... it's most likely related to how we choose to identify ourselves by the choices we make and the groups we associate with. By attacking a part of the group, it's attacking what defines the identity of these people even though they are not racist, sexist, homophobic, xenophobic and/or Islamophobic. (Those being the things mentioned in the speech.)
Although, as someone that grew up in eastern Pennsylvania and now lives in the south, apart from Philadelphia and Pittsburgh, Pennsylvania seems far more like a southern state than anything. So, the push toward voting Republican doesn't surprise me much. It's really the large metropolitan areas that made it more of a Democrat state anyway.