I believe that the left is focused on a wider context and trying to ensure that the worst moments of human nature are not repeated.

(preface: not saying this is going to occur or repeat etc but-) I believe everyone here would not want genocide, rape camps, slavery or other atrocities to exist (they may very well do so today, but we can also hopefully agree this is something that is to be avoided as much as possible).

"The left" is fixated on this. The context of "how did I get here?". How is it that I am having dumplings delivered to my door while there is starvation still rampant in the world? These questions lead to the thread pulling of context and it's interplay with the current circumstances of the (left-leaning) individual.

From here this leads to history, oppressive and forceful spreading of Christianity throughout the world through often violent and culturally dismissive means, exploitation, and the above atrocities.

The left is predominantly concerned with not repeating these same mistakes. While they do suffer from some of the issues that affect "the right" voters - I would vouch on a general scale globally not really as much:

The right usually work highly volatile positions which they are sold as (and rightfully so) adding to the prosperity of their nation and fulfilling of a duty, they feel (also rightfully so) like fodder used by their nation for economic gain and prosperity. The right voter base will react against any entity that is destabilizing this - it is unfortunate that they are treated as such with no opportunity for transition when the industries predominantly aligned with these groups are by their nature bound for a temporary life time.

While the left does often experience the same hardships of economic immobility, job loss, they can abstract themselves from this with the often larger city centres offering alterntives to these downturns. The right is unable to do the same.

I am of the opinion (emphasis on opinion in these very volatile areas that we have to apply utilitarian laws to) that Christianity/left-values are - as you said - group identifiers that allow a sense of belonging.

I personally am left leaning so disagree with the assessment of "legitimization" of Christianity when there are several open cases of heinous instances where it hasn't afforded the same - and has resulted in a highlight reel of the worst humanity has to offer (not isolated of course to Christianity, but it is a hard case to sell that solidifying this group will result in net positives, especially when blatantly used as a tool by politicians to consolidate their own power). Along with this, certain issues regarding race, gender, and other imagined hostilities seem to be purported by 'the right' as concerns, when in reality we are simply serving to undermine the countries we all wish to be their best. We should be openly encouraging performance from skill and shaking our heads at those who would lower another's potential by a bizarre rubric. While there is much to be said for the benefits of community, there is simply too much castigation from the right to misdirected or non-existent perceived threats. As you said "there is no shame in wanting a group identity", I believe that this metric should then be used to not demonise females wanting to belong to "feminism", Latinos wanting to belong to a Latino identity, or the many other groups who have been - throughout history - actively suppressed either through violence, genocide, or structures in place that do not afford them the same opportunities being demanded now. To ask for legitimacy whilst ignoring past (extreme) grievances when the same was requested and then crying foul is remiss.

However I believe that across the globe that left-leaning parties need to do much much more work at re-training, re-educating, and emphasising just what tremendous effort the blue collar - and often right-voting - people of their countries have sacrificed so that the left get their opportunity to learn and mobilize upwards. There is a need to bring them along as well or the country is just as doomed and suffering of citizens just as bad.

We need to work together, support each other, and not be drawn in to crude openly-acknowledged-as-broken party systems.

That being said - if Trump does not destabilize this system in the US and push the country toward a preferential system, he isn't worth the square inch of a used toilet paper. (one final left-leaning comment in there!)

P.S. I genuinely hope he tries to "shake things up", however all rhetoric points to him being more fascinated with self-service - even above those issues of the hard workers in the centre of the US that supported him with their hopes on the line.