Unfortunately, you will never be able to prove this to CRIMINAL law standards, but 0 to 30 overnight for a NEW email address is one HELL of a coincidence - spam levels tend to grow steadily, increasing with both the length of time the email address has been live, and the amount of exposure it gets over the internet. The alternate explanation would be that the email address was harvested by malware, and propagated through a spamming botnet, coincidentally on the same night as you sent your riposte to the casino support staff.
If they are, they are VERY good at hiding it. Go Wild seems to have the ability to manage casinos "in the Go Wild group", but this "group" currently has only the one member, Go Wild.
If these really are white labels, maybe they can be traced to their sponsoring group. As for "years of experience", this means nothing, this is what players heard when Hippo Jo launched, and looked like being a good RTG to play at.
Maybe the experience was not in the relevant field, as surely someone with experience of online gambling would have seen the dangers in the initial launch offer of 200% up to 600 credits, with VERY generous terms too.