I don’t consider myself a Christian anymore, but based on what I was taught as a kid, I’d personally take anything that wasn’t explicitly stated to be spoken by God or Jesus with a grain of salt, especially when it comes to books that weren’t written by Jesus’ disciples (excluding Saul/Paul, who never actually met Jesus).

As a kid, I was taught to read the Bible and use my brain (god gave you one, use it) to figure out what it was trying to say, not blindly follow it without question. The reason for that is because I was taught that the Bible is inspired by God, not written by him (unless explicitly stated that the passage came directly from God or Jesus’ mouth). As such, you have humans attempting to understand God’s (and later Jesus’) commands, which means they aren’t always going to be 100% correct and/or there may be historical context that is missing when you take it literally and at face value.

You’re supposed to not just read, but also think about the Bible and decide what parts make sense when taken in context with what is said to be explicitly said by God (it’s part of the reason why some Bibles mark anything said by God/Jesus in red).

For an example, the passage you’ve quoted could be interpreted as a warning about pagans larping as Christians to take advantage of christian kindness and distort the word of God into something else (similar to the merchants in the temple, or like what is happening in Christianity now). You could also read it as an almost complete reversal to what Jesus taught in the early NT.

Which one of these makes more sense?

A) Jesus comes to earth, teaches people about kindness and goodness, hang out with prostitutes and untouchables, dies on the cross for everyone’s sins, becomes a zombie, and declares that the laws of the Old testament had been fulfilled through him so all could be saved. Then a few years later, he changes his mind and inspires Jude to write a letter about how the gays should be cast out and are going to hell.

B) Jude was writing the letter as a warning to keep your guard up around non-christians in case they might persuade you to distort the teachings of Jesus and/or hijack Christianity to turn it into a money-making scheme. It wouldn’t be the first time it happened (the merchants in the temple immediately springs to mind again).

Or C) Jude didn’t really know what he was talking about and the book/letter is included because it’s referenced in other places of the Bible and theologians would rather err on the side of caution and allow a non-canon book to be included in the Bible than delete something that might be important (iirc the Bible states that you’re not supposed to remove, change or add to anything said in scripture, so from a Christian perspective, I’d imagine if you’re not sure about something then it’s probably better to include something than exclude it).

Imo, B) seems the most likely. If you believe the Christian God is real, then A) is absurd, and C) seems unlikely due to Jude’s proximity to James. It seems like if C) were true, then there would be records of Jude being refuted or rebuked.