Since praxeological reasoners are neither Left or Right, perhaps we would be objective in judging both.
In that respect, I’d say that the Left is the most self-flattering side of the spectrum. One might even say that they have constructed a proud self-flattering mythology, of all their proud battles and successes.
Tony Blair, whenever faced with harsh questions about the failing National Health Service system in Prime Minister’s Questions, would always counter Liberal and Conservative opponents with a reminder that “We, the Labour Party, created the NHS, and we are the ones who have kept it functioning properly”. No matter how many reports of the year-long waiting lists for cancer patients who die when their turn comes or how many reports of people who get sick from unsanitary rooms in NHS, Blair always touted the system as a crowning success of the Labour Party, which should not be criticized for petty shortcomings like public hospitals killing patients.
The American Left is always proud of how its peaceful protests produced the Civil Rights Act…peaceful protests that turned into violent riots in Detroit and various rich upscale cities of US, with knives and machine guns becoming the new political arguments. It’s always the CRA itself that is glorified, not its actual effects - the spontaneous increase in poverty and social immobility of black Americans.
The American Left also is proud of having started the New Deal and entering WW2 - both of which had destructive effects on the US, with the New Deal lengthening the Depression and WW2 impoverishing Americans at home and killing millions of Americans abroad; all of it just to strengthen Stalin and give him half the world.
The American Left is proud of its antiwar movement in later years - except when Lyndon Johnson started the Vietnam War, when Clinton aggravated the Bosnian war, and when every major leader from the Left only fought unnecessary wars, rather than stop war. Indeed, the Left has lost its interest in antiwar stands, as Barack Obama butchers hundreds of Pakistanis, with not one word of protest from the Left.
The African Left glorifies men like Kwame Nkrumah, who quickly turned his prospering nation into one of the poorest countries in the world.
The South American Left glorifies child murders like Che Guevera, and thinks that the anti-imperial totalitarian authoritarianism that arose in various South American nations actually helped their countries. Of course, not only did Leftist dictators butcher many and ruin lives of countless others, South America never won the anti-imperial struggle. Even with Chavez and Morales doing all they can, South America is still a playground for the US, and both their and other countries in South America are freely kicked around as often as possible by the US. There has been not one single success in ending US imperialism in South America. Not one.
The European Left glorifies its high unemployment rate, low growth, destructive social engineering welfare state policies that have left France and Spain as broken state-financed nations
Ironically, the Right never glorifies any achievements. Indeed, the Right claims perpetual failure against the Left. It has a more pessimistic tone, about the failure and decline of their society. Some members of the Right claim that society started falling apart in the 1960s, some say in the 1910s, some say in the 19th century, some even say in the 18th century. The Right always talks about what went wrong and who did wrong.
But I must admit: what self-flattering myth would the Right ever have? “We successfully killed millions of communists during the Cold War under dictators like Franco and Pinochet.” I guess deep down, the Right knows that it should be a little more humble in claiming to have done anything.