I used to work in renewable energy, and every time we started an initiative for a new wind farm we would meet extensive resistance from the local community. So we had town halls to try to give them comfort and at those town halls there would be a vocal minority who dominated the meeting with ignorant fear and bias. One thing we quickly learned was that our logical replies had nigh on zero effect on these people, BUT the debate did have an impact on the silent skeptics. Gradually they would grow to accept the project, and over time they would embrace it.
Wheaton's pessimism is because he is focused on the vocal minority and not the silent majority of the opposition. That is not the right place to put your focus.
We are gradually seeing a steady decline of support for Trump. I read this week that there are currently more people in favor of impeachment than there was under Watergate. The Republican health care plan has only 16% approval. Even among Trump's constituents the support is only 25%.
WW2 lasted 5 years, Watergate 2-3 years. We need to be steadfast and keep pushing, keep challenging, keep pushing for "nation over party", keep supporting the media and NGOs, keep chipping away and not lose the will to fight. I think we can still get there, and pessimism certainly won't help.