Just because it's legal, doesn't mean there's no victim.
>and I think it's pretty silly to say there's a victim when I have a beer at home after work.
This is getting into hair splitting territory. Meth has therapeutic value. It's available as a prescription drug under the name Desoxyn, and it's indicated for treating ADHD and obesity. It's possible for someone to get illegal meth and use it to self-medicate their ADHD responsibly, but that's not the typical use case. The typical use case is someone taking far above the therapeutic amount, getting tweaked out, and engaging in harmful behaviors that hurts them and their community. Sure, you could argue that using the drug itself isn't harmful because theoretically you could be using it responsibly, but it quickly leads to a slippery slope. Is driving drunk victimless, because if you don't crash nobody is harmed? Is violating health codes victim less as long as nobody gets sick?
We have no idea how many people would be using it responsibly in other situations but the current one so your examples are flawed.
The whole reason addiction is a problem is that it alter decision making, once someone is addicted. So you incur much of the moral responsibility the first time you decide to take the drug for fun.
And also, opioids are a curious example for responsible drug use, given how many people who used prescribed painkillers became addicted to them.
This is true, but there are many things people can become addicted to and only some of them are illegal drugs.
Using meth is as victimless as using alcohol, and I think it's pretty silly to say there's a victim when I have a beer at home after work.