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.)
I love when they pretend to take the side of the worker by pointing out that it's the restaurant who is screwing their servers by underpaying them and making them rely on tips, which is of course 100% true but you're still eating at the restaurant.
I don't like tipping culture either, so I just... don't eat at restaurants. I actually don't need food slaves to serve me.
reject pizza slavery
embrace BMF thought
Is there any political group working specifically against tipping?
Questioning how much not eating somewhere actually moves the needle at all. If a restaurant goes out of business, it's not necessarily clear that it's because patrons opposed tipping culture. So for that reason, it seems that anti-tipping progress has to come from labor itself, by refusing to work for tips. But I also recognize that that's not possible for many people barely scraping by.