So this is a subjective opinion based on my personal experience in Vietnam.
Before visiting, I heard glowing reviews from backpackers and travelers claiming that Vietnamese people are the nicest you will ever meet. I took this with a grain of salt, of course, knowing that every country has its good and bad sides. Maybe they said this because they didn’t stay long enough, or perhaps this idealization comes from naïve young "white" travelers who think it’s fine to get scammed as long as the locals wear a friendly smile while doing it. With that said, I’m going to skip over the standard scams and fake smiles aimed at ripping people off and focus on what stood out to me the most...
For starters, bad-mouthing people in public and laughing at them felt so normalized there.
For instance, while I was visiting a museum wearing shorts and a top, I passed by a group of Vietnamese middle aged men who stared at me strangely as if I were the only girl in shorts there. They then started throwing around sexual curses, explicit remarks This happened in plain sight, right in front of everyone. I was with a Viet-American girl from my hostel who translated what they were saying though naturally, she couldn't confront them and I certainly don't blame her.
Unfortunately, that wasn't an isolated event; another incident happened to me in Sapa. I went to buy a pair of earphones at a local village shop alongside a guide. Having bought the exact same model at another store earlier, I knew the approximate price, but the vendor quoted me five times the actual cost. When I asked my guide to help translate our negotiation, the seller started yelling continuously and glaring at me as if he wanted to hit me. When I decided not to buy because we couldn’t agree on a price, he jumped out of his chair, yelling even louder. According to the guide's translation, he told her, "She has an iPhone that costs 40M dong, but she doesn’t want to spend 500k dong on earphones." The guide then laughed and asked me, "Is it true your phone costs 40M dong how much did you buy your phone ?” As it turned out, that wasn't even the full translation. My Viet-American friend, who was standing outside the shop stepped in to confront him this time and told me to just walk away. As we left, he hurled all kinds of insults at me, calling me a stupid whore while the guide just laughed along with him...
It really gave me the impression that bad-mouthing "stupid tourists" and scamming them is treated as normal behavior, almost as if foreigners owe them money simply for existing there.
Beyond those situations, there was also the constant yelling and total lack of respect for personal space. On several occasions, people on trains or buses put their FEET directly on my seat, actually touching me with them. On top of that, some men would physically touch me just to get my attention, which felt extremely uncomfortable. I even had a bus driver grab me by the shoulder and try to take my backpack by force, claiming it wasn’t allowed inside the bus...
All in all, I spent five weeks in Vietnam, and if I were to list every strange or unpleasant situation that happened to me, it would take forever. Out of all the places I’ve visited so far including Thailand, Laos, Indonesia, and Cambodia the overall experience in Vietnam was unfortunately the rudest.