There is a saying that goes by "Never attribute to malice that which is adequately explained by stupidity."
I do think that the vast majority - if not all - complaints are genuine in a way that the person complaining feels like they got cheated/mistreated by the casino. I am sure the feeling itself is very real, although there is a high - about 50% - chance that the complaint is actually invalid.
Can't we say that it is malicious that some people are making accusations because they want to harm the casino? It is no less evil if someone does it because of some dissatisfaction after losing money in the casino. There are people with real issues and ones with invalid complaints, but I just wish to remind you about the third group of "paid trolls & people who can't accept when they lose".
I think that the low effort, invalid complaints are more akin to rant posts, than actual accusations, even if they call it as such.
If you want people to take you seriously, you have to tell your story and show some evidence (screenshots, conversation with the casino team, whatever you have). Just words can help, but if you have a good reputation... that comes with time & activity. Trusting someone you don't know is not wise, especially if we have only his words.