Maybe you're in a bubble in terms of knowing how people feel about out-parties, as your descriptions of right-wing parties are too caricatural for you to not be biased. I'm in the same bubble and don't think most people view things that way.

Your point about skewed results is right though: reading through the paper's annex on dataset construction, no distinction is made between out-parties. An analysis based on political spectrum-based clusters of parties would have been more telling, though the current methodology is probably on point for the more echo-chambered people.