I am not European, but you could point out how anti-Romani sentiment generally seems to border on fascist levels of dehumanization and seems to justify genociding them (ignore them when they try to put on a "righteous civilized person" act because they are just being racist in a backwards way), and compare it to how Jews were once seen as people who would take over the world. Also, keep pointing out the bigotry, because consistently pointing out the racist undertones of their rhetoric will convince some that maybe they should not believe in fascist rhetoric.