For me the easiest tell is the up front, unprompted, and unsolicited declaration of nonpoliticalness. When someone takes the time and expends the breath to announce how nonpolitical they are, what follows is almost always a rant about how everything/everyone else is too political these days, and that of course leads into something between status quo advocacy and outright reactionary/regressive sentiments for some fabled time before those wicked politics were visible to the nonpolitical ranter. 
People that are hostile to service workers. Some just want to take some ideological stand against tipping when the service worker doesn't really have a choice and needs those tips to survive in the current unjust system in a way where ideological purity gestures toward that service worker just look like being a greedy and sanctimonious asshole. The worst of such people will actually declare, shamelessly, that they believe that service workers don't deserve a living wage. The implications of that are 
worthy.
I may get shit for this, but I'll say it anyway: this hair and beard combo, seen on living people. 
I have yet to meet anyone in person with that look that wasn't a chud.
(If one of you is a comrade with that look, I am sorry in advance for the prejudice and if I ever meet you in person I will atone by buying you a drink or something.)
Just ask them about all the homeless you see around town. This is the American equivalent of asking a European about the Roma
it's honestly amazing how quick a lib will start to call for death camps when homelessness is mentioned. is it different in Europe? serious question, does the presence of some kind of real social safety net mean that people are less bloodthirsty to their neighbors just for being poor?
Europeans will pretend racism is an American phenomenon, despite the roots of it coming from Europe, until you start talking about Roma at which point they become as racist as a klansman.
I dunno, in my experience European racism is a more primitive type that you don't see as much in America anymore. Like even the most feral American hogs usually do the pretend song and dance that racism is bad before they beat the insert slur here to death. Like not saying it's better, just the pretension that Americans are somehow uniquely racist seems like eurolib cope to me.
I think it is that racism is so baked into American society that it is hard to miss I mean a nearby country club, which cannot be turned into public housing fast enough, had to be sued to let in Irish Catholics in the 1980s so it is harder to deny here. As aresult more Americans are aware of their racism than Europeans.
There's really no way for liberals to win with this one because their wealth is predicated on rising property values—which naturally produces homeless people. If you even adopt the milquetoast liberal approach of constructing affordable housing, that lowers property values. If you just pretend the homeless people aren't there, that lowers property values. So as a liberal, there's really nothing you can do. Capitalism has fucked the planet for the last couple of centuries; now this monster, in its vicious hunger for ever-dwindling sources of profit, is finally coming for you, too. The death camp approach is also pointless (purely from an economic perspective) because rising property values will continue to produce homeless people, which will mean more tax money for death camps, which themselves will produce ever-larger numbers of radicalized people who will increasingly adopt violent and organized methods to oppose you, etc. The only way to deal with "the homeless problem" (actually the landlord problem) is to eliminate landlords and establish quality universal housing—which means that dwellings cease to be an investment and you, Mr. Liberal, have to actually get a real job and work for a change.
The bourgeoisie wouldn't mind doing another holocaust.