That can't be the difference. Assuming parent poster is talking about gambling hurting people (and ignoring that gambling and most other addictions do hurt others, as siblings pointed out), then banning of hurting others you would mean banning bookmakers, not just their advertisements. Parent was specifically banning advertisements but seemed to be saying to leave gambling industry legal.

I could see the way to argue for banning advertising being along the lines of minimizing harm. You acknowledge that gambling does hurt gamblers but also people close to them and society more broadly, but that prohibition may not be very effective so you permit regulated legal gambling (but no ads). I just don't really see how you can make it a freedom argument.