The same people that I have seen rage against other people gambling will also argue in favour of legalising drugs which are more addictive and can cause psychosis.
In addition, making it illegal does not stop actual addicts gambling. You can go offshore and get completely unregulated services, that comply with no regulators on harm prevention. The US was the largest sports betting market in the world when it was illegal in every state bar Nevada.
Also, online providers maintain lists of self-excluded people with state regulators (to be clear, the state holds the list, people put themselves on the list and are banned everywhere). Casinos are significantly less regulated in this area because, due to the nature of the product, is not possible to put in limitations to the product (for example, reality checks, loss limits, giving you access to data on your usage).
All regulated sites have third-party verification of their games by specialist testers and state regulators. Every change to every line of code that touches a regulated service is reported. It is not possible for operators to lose at casino games because of the scale, and you think they are willing to destroy it all to get your $10 faster?
The issue with online gambling is: some people cannot resist telling what other people (usually people poorer than them) what to do, and some people have not thought the alternatives through.