Fritz Fischer was a German historian who focused on WWI. Many German historians had argued that Germany only had limited responsibility for WWI but Fischer found a significant amount of evidence to the contrary. When Fischer published his work he was attacked by other German historians.
A more in-depth look at the controversy: https://www.historians.org/publications-and-directories/perspectives-on-history/march-2000/in-memoriam-fritz-fischer
This RLE clearly shows how nationality can lead even professionals to come to conclusions that seem to conflict with the evidence. German historians may have been focused too much on agreeing with German peers or with reaching conclusions that made their own country less responsibility for WWI.
The “ourselves” in November 2020 TOK Essay Prescribed Title #3 in this RLE could be interpreted in a nationalistic way.