That need is where the moralizing comes from. As the piece describes, there are swaths of people who are left behind by difficult gaps our societal culture - but there are also people who are either ignored or explicitly oppressed by our political system too.
The "evil" in the oppression part is easier to explain (though more divisive) - in modern US politics, Republicans are almost universally hostile towards and opposed to expansions of rights for marginalized groups. LGBT+ rights are an obvious example, which they have almost universally opposed. Yes, Democrats have also opposed things at times and acted slowly, but over time the party has changed to accept them, and Republicans have not. Whenever positive change is made, it is almost universally by Democrats against Republican opposition.
The ignorance part is trickier. As a conservative party, the core Republican demographic has always been the idealized social norm. Almost by definition, maintaining existing social norms is what a conservative party does. In pre-modern US politics (say, pre-1970s), that would be the middle class, straight, white, Christian, male. Because that is the base, that is the group whose interests the party serves. Thus, a blind spot is formed that excludes everyone else in society who does not fit that mold. Generally speaking, their needs are ignored - even fought against, if it would cause disruption to the social norms their base represents and values.
Ignorance itself is not evil. But sweeping known problems under the rug is. Over the last few decades especially, we have learned a lot about the problems of our fellow Americans that have been ignored by society. Minority discrimination, marginalization, extreme wealth inequality, lack of healthcare access, mental health problems, etc... And again, Republicans are almost universally against any change that would alleviate that suffering, usually with the excuse that they are too expensive (e.g. healthcare) or are not real problems (e.g. BLM). The real reason, though, is that any such change might cause discomfort to their base - rich white people who don't want to pay taxes (and the people like the kid in the novel who are manipulated by them).
As society learns more about the people who it has left behind - exactly as this article details - it becomes a moral imperative to fix those problems. Republicans have been purposefully obstructing progress for decades - Gingrich and McConnell have literally bragged about it.
As social media connects us more, the stories of the oppressed and marginalized become louder and more apparent. As this realization becomes more clear (as some would say, "becoming woke"), the urge to fix it becomes greater. At this point, there is no longer a reasonable justification for inaction. Combined with the growing influence of the racist alt-right and clear escalation of anti-democratic practices, it is difficult to characterize them as anything other than "evil", particularly if you are (or are allied to) any of the groups that they harass or dismiss.