Greetings,
There's nothing wrong with slang in itself - it's a natural development of any language, after all. It's just that people forget what the actual purpose of slang is. Slang is intended to be used within groups of people who mutually accept and understand it. For those within such a group, it's a way of reinforcing their bond to each other. For those outside that kind of group, though, it's an alienating use of language
This means that some users are depriving themselves of having their opinions heard, simply because they can't bring themselves to write in standard English. If you want your ideas to be understood by as many people as possible, there's only one option: use the most expressive language known to humanity - English.
Peace