I want you to consider the two states of reality from before OP deposited to after OP was returned money.
Prior to deposit: No bets have been made. Balance is X.
After return: Bets have been made. Balance is X.
The fact that Sportsbet.io accepted bets means that they were willing to take the player's money in the case of a loss. Given that the player has instead won, the casino is now instead liable to pay up. Unfortunately, due to them using their arbitrary ToS, they are able to quote a clause that gives them absolute discretion and they are able to essentially nullify the player's wins.
Now imagine this.
I offer you a bet. If you win, I freeze your winnings and return your deposit. If you lose, I take your money. I cover details allowing me to arbitrarily freeze balances if I consider you a negative to my casino in a clause outlined within the ToS. You agreed to this. I can now act accordingly to everyone else who agrees to the ToS, because of course, contracts are all-encompassing and if you were too stupid to read it then you deserve to get scammed.
The player apparently made at least 50 bets, some of which were wins and some of which were losses. So the net amount won is what he is claiming to be the "amount scammed." Of course I disagree with the word "scam" here because that implies a net monetary loss, which didn't happen no matter how you frame it. Its arguable that he was scammed out of his time or the money he could have been up by placing the same bets elsewhere (if that was an option).
In your scenario, you sound like you're describing a sportsbook that I simply wouldn't play at, but I don't think Sportsbet sees their decisions as "arbitrary."
You see them as arbitrary.
This is what it looks like when Sportsbet is actually trying to dissuade players that cost them money, and not because they were violating Terms of Service:
Some bookies don't want you at their site no more. My account at Sportsbet is limited to ridiculously low amounts, I have no price boost anymore, even my max bet button is gone. They want to get rid of me and achieve that by making my account unusable. If multi-accounting was allowed, they couldn't get rid of me (or not that easy), since I could just open new accounts all the time. This is industry standard and they have all the right to do it. I am ok with it, though it's a bit annoying always I must confess, but nothing I can do.
Ty also has a great point about how most casinos/sportsbooks view multi-accounting:
There is multi-accounting and multi-accounting, this is the bottom line. If you are multi-accounting, but always lose all your money, then you are allowed to multi-account. If you are multi-accounting and winning, then you will be a victim of T&C's.
I am 100% sure that every casino/bookmaker knows about a lot of players doing multi-accounting at their sites - and they are fine with it, as long as it's giving them profits. If these players start to win, hit a bigger parlay or request a withdrawal, they can always user their power-tool, so this is a worthwhile, nearly risk-free, business, where you can never prove the operators being guilty.
Sportbet's behavior here is pretty standard in the industry. I had to forfeit casino winnings once because I forgot I had opened another account there years earlier, never activating the bonuses from either. But the casino put 2-and-2 together and took my winnings. I was pissed, but technically I did violate their ToS, so I accepted it and moved on.
Ultimately its up to the player to find a new casino/sportsbook if they feel they have been treated unfairly or wronged. I draw the line at confiscated deposits, which is one of the main differences between a reputable and non-reputable bitcoin gambling operation, exchange, wallet service, etc.
Not that I think you forgot it was an option, but if you really feel strongly that Sportsbet is in the wrong then you should support whatever flags against them you think are most adequate.