You can't siphon a trucks gas just because it has a blue line flag. Most modern cars have an anti-siphon valve, so that causes issues.
Instead, you locate the fuel tank and drill a small hole in it. That way you can let the fuel collect in a tub or jug. On lifted trucks this is even easier. Drill the hole, pop a large jug under it, perhaps use a small rubber hose or funnel.
Remember to leave them a little note that you've drilled a hole, so they can go get it repaired and not leak fuel everywhere attempting to refill it.
Is that why I couldn't siphon my gas that I needed for a generator after a hurricane? Not only did I fail at what I thought would be an easy task, I got sick and threw up in my 95⁰ house
Pro tip for sucking volatile gases, you can suck air into your mouth and push it out your nose without it going into your lungs. I do that when I clean glass pieces with iso when there's still some vapors present. If you exhale out your nose while you do this you can be extra sure none goes into your lungs. Granted you should also be sure you're actually pulling liquid if you're trying to syphon, but at least you wouldn't be pulling into your lungs.
Yup, you got a lung full of gasoline vapors and nothing else. You need a car siphon pump, they're super cheap and available at any auto store. You just gotta make sure it's got a long hose on both sides and a tube for air to get into the tank. If the hose is too long just cut it. Those stick ones don't work on every car cause some gas tanks have slight bends.
In case anyone can't tell this is sarcasm, this (intentionally causing damage to private property belonging to someone else) would be considered vandalism, which is a crime. Please do not commit crimes.
Step 1. Poop in a bag.
Step 2. Grab the bag from the bottom and pull it inside out so it's now acting as a poop glove.
Step 3. Shove the poop under their door handle and then use the bag to wipe excess visible poop away.
They might not know it's because of their boot licking but they sure as hell will start thinking about things a little more.
On a more serious note, though, while I do 100% that the "Thin Blue Line" is pure idiocy, I don't think that actually going out of your way to harass them (even if it is warranted) is in any way effective in convincing them otherwise and having them see reason. Same reasoning as with why many young boys these days fall down the alt-right rabbit hole and become a Tater Tot.
There is a high chance that someone shoving that thing-blue-line bullshit probably own a gun and are desperately waiting for an excuse to shoot someone for even the most minute reason. And they had said "FAFO" 3 times already that day
You also think beating up fascists is "a bad way to make them see reason"? It's entirely not the point. You beat up fascists to make them be afraid of openly being a fascist.
Fair enough, I was being too idealistic. I just wish we can have them see reason instead, but if we can't, making them shut up and not spread their idiocy would perhaps make for the next best thing.
A Tater Tot is a mindless follower of some very punchable asshole called Andrew Tate. Also in regards to your second point, while that is true, they will and already do have that stupid stereotype ingrained in their racist minds anyways. Might as well take advantage of it.
This flag is called "Thin Blue Line", which is a pro-police symbol. The origin is from the thought that supposedly the only thing keeping peaceful society insulated from total anarchy is a "thin blue line", or a small number of law enforcement officers who voluntarily put themselves between the two.
However, as noble as the origin sounds, the flag itself is only a modern artistic creation that can trace it's actual creation to the counter-protest of the "Black Lives Matter" movement in support of the police (the ones who were the subject of accusations of racial bias and discrimination against blacks in America) and it often interpreted as a racist dogwhistle, supporting acts of police brutality, extrajudicial killings, and authoritarianism in general.
It's a pretty right-wing affiliated symbol and you see it in conjunction with a lot of other conservative virtue signaling, iconography, and stereotypes.
The thin blue line is a symbol for the police. Used in the UK and US.
As a reaction to Black Lives Matter protests against racist police brutality, the (far-)right coined the term Blue Lives Matter to protest violence against the police.
Of course, the whole thing is disingenious. They support the police because the police in the US are often racist and they like that the police disproportionately beat up black people. When rioters stormed the US capital after Trump lost the election, plenty were waving blue lives flags, and didn't actually seem to care that much about endangering the police guarding the building.
TLDR hyper-partisan US political virtue signaling associated with the far-right.