Nationalism in itself is not an ideology itself, so instead it is seen as something which has to tack on to another ideology. That's why we've seen things ranging from National socialism to National conservatism to even extremes of Fascism which has nationalism as a far part of its ideal. I will say while there is nothing wrong with being proud of your heritage or being proud of your country, when it goes into nationalism, a blind loyalty and a superiority complex relating to other groups, that is dangerous. Because that is often what a lot of these dictators hold onto to gain power and influence or even justify genocide.
Did we go "HEY WE AGREE WITH THOSE GUYS?!" No. Take a look at the chart a second time. It isn't just "left and right" it is also vertical and most of those leaders are very much high north on the spectrum. I don't think anyone is near them No matter how you slice it, being an evil person is beyond just what your economic beliefs are. Killing a shit ton of people and establishing dictatorships? Yeah, that's evil.
Take this quote from Thoughtco.com
"The main difference is that under communism, most property and economic resources are owned and controlled by the state (rather than individual citizens); under socialism, all citizens share equally in economic resources as allocated by a democratically-elected government."
Then another example from the site, describing "Democratic Socialism"
"Democratic socialism is an economic, social, and political ideology holding that while both the society and economy should be run democratically, they should be dedicated to meeting the needs of the people as a whole, rather than encouraging individual prosperity as in capitalism. Democratic socialists advocate the transition of society from capitalism to socialism through existing participatory democratic processes, rather than revolution as characterized by orthodox Marxism. Universally-used services such as housing, utilities, mass transit, and health care are distributed by the government, while consumer goods are distributed by a capitalistic free market.
The latter half of the 20th century saw the emergence of a more moderate version of socialist democracy advocating a mixture of socialist and capitalist control of all means of economic production supplemented by extensive social welfare programs to help provide the basic needs of the people."
The second paragraph is probably closer to what some people here maybe say as an idea Did anything there reference "Hey, let's kill people!? Hey, let's be racist as fuck!?" No. There are other things beyond an economic view that cause people and countries to do horrible horrible things.
I mean, I studied and have a degree in political science, so A: I have better than average knowledge of this stuff (not saying I can never be wrong, but I at least have some grounds of knowledge) and then if you pay attention to some of the earlier posts, it shows that along the "spectrum" there are a wide array of ideologies. It is possible for people to be near on the spectrum but has some disagreements. Even then, a political test like that presents an average. Someone may have stances on certain things which may contrast a bit with people near their spot on the spectrum.