@thomassowell123 Hmm it looks like I didn't read the Lichess rules carefully, thanks for letting me know. It looks like my opponent was that type of "person" you were mentioning, and I got a warning from lichess as a result.
I saw one of the titled WFM players give their opinion about cursing. I disagree with the WFM. Cursing is not representative of whether a game has broken my ego or not. There's no reliable way of telling whether a person has their ego broken unless you are there in person. Cursing is just another way of expressing emotion, especially after losing to flagging when in a completely winning position. Now if a person gets hurt because of a type of language, then they can simply leave, it's not my fault.
Even though this is apparently an unpopular opinion in this forum, I do not think flagging is acceptable in many different scenarios. Especially when a player uses a lot of time to make brilliant or excellent plays or defend a losing position and turn it around to be winning, or in a theoretically drawn position. I also think that it comes down to the personality and character of the player, and whether they want to uphold the virtues of sportsmanship and respect in the world of chess esport where anonymity is prominent. I'm not saying that there is no respect in online chess, but I think that we should all make an effort to commend players that make good play, and resign in completely lost positions or agree to draws where necessary in blitz no increment. I just think that it's a cheap way to win and gain rating points that doesn't require much skill than just premoving random moves (in blitz). In bullet, time becomes a much more important factor than in blitz in my opinion.
I agree that time management is important, and this is especially important in variants like bullet.
But in blitz, at what point does flagging become acceptable and unacceptable is a fine line, and it will ultimately come down to the situation at hand. If it's a tournament and your game is the deciding game, then maybe it is acceptable? What about just casual single matches?
TL;DR I completely disagree with anyone on here who says flagging is "part" of the game in a blitz no increment game. I don't care if it's increment or no increment, flagging is not something that anyone should be a proud of, especially when doing it in a losing position in blitz. (Please keep in mind that this opinion is based around blitz, not bullet).
I created this forum post because I wanted to gain everyone's perspective on flagging in blitz. I didn't want to fall prey to confirmation bias or other biases, so I wanted to get everyone's position on this topic. After reading everyone's replies, I still remain by my conclusion as written above, even if it is not popular. This opinion does not reflect the type of person I am in real life, and it's just how I stand on this issue. Thanks for everyone's replies!