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.)
Being afraid of Chicago is a pretty good (though not perfect) tell about where they're getting their news. A lot of right-wing sources will go full
Being afraid of cities in general, especially if they live in a small town/rural area.
"B-b-b-but the fascist TV man told me cities are warzones full of minorities and the homeless! Everyone is constantly robbing each other and murdering at random! No I haven't left my hometown of 2000 people in 15 years, why do you ask?"
I can't tell you how many people I got this from when moving to Minneapolis
It just means I see fewer of those people around 🥳
Being afraid of Malmö is a similar kind of red flag.
For Germany, it's Berlin-Neukölln. However, there's less of a "this is a dangerous no-go area", and more of a focus on supposedly super-strong arabic "clan" families, which are known as dangerous criminal organizations and there are consistent raids against in all of the country.
Who cares that the N'drangheta (calabrian mafia) has been way more successful in weaving itself into the German Economy, it's a good occasion to scaremonger among BILD (right wing tabloid) readership.
Well that's the thing, German conservatives see somebody doing a giant money laundering operation and will immediately feel a deep kinship to them. Bourgeois politicians are obviously always close to white collar crime, but the CDU/CSU just loves that shit, it's their biggest passion.
I have every right to be scared of Chicago because I had a flight with a layover there last week and as soon as I walked off the airplane and into O’Hare airport Chief Keef ran up and shot me to death
I've been living there my whole life and always check under the bed for Chief Keef before going to sleep.
You never know.
Y'all still checkin for Chief Keef? Man I'm lookin for the Ghost of King Von
And no, I'm not from 63rd in case he's here