You are right and I completely agree with you, for trustpilot to delete 1xbit review page from their website will be the worst thing for them to do, and this equal to denying customers or potential customers access to information that would have possibly help them in their decision making..
Trustpilot have no other job they are in the web to do, other than to allow internet users access to genuine reviews of web services, which also makes navigating the web easier and safer for most people, when they have a service like 1xbit on their platform, and users of this service are being scammed on daily basis, it is their job to inform and warn users visiting the 1xbit review page to stay away from 1xbit, or the make the statement more formal, they could say that they have received numerous bad reports about 1xbit, and that visitors are advised to be cautious in dealing or transacting with this casino - this would be better than deleting the 1xbit page as doing so will only make 1xbit even more stronger in their scam activities, and trustpilot could be seen as an accomplice if someone would drag them to court and the matter judged fairly.
To be fair, I have also noticed the problem with review websites are not exclusive to cryptocurrency casinos. The other day I wanted to check out the reviews about Binance on Trustpilot, I thought I was going to find mostly positive reviews and experiences, because we all know Binance is a legitimate service with no reason to scam their customers.
Imagine my surprise when I find there are a very big percentage of negative reviews about Binance, when I started to read them I realized all of them were false negative reviews done by scammers. The scam was to falsely leave a bad review saying they lost their money in Binance for whatever reason and managed to recover all of it thanks to some "professional Bitcoin recoverer" and leave their contact information there.
The idea is to catch the attention of anyone there who suffered losses because a ponzi or scam, so their grief can be further be abused by other scammers.
In general, I would say Trustpilot is not a reliable source of information if we are trying to know whether a service related to Bitcoin or cryptocurrency is legit or not. Shillers will always leave false positives and scammers will leave false negatives.
Bitcointalk by itself (not even being a dedicated review site) is already one thousand times better than TP.