Writing software isn't illegal. Timeline goes like this:
1. Developers write open source software
2. Open source software is deployed for money laundering purposes by other people
3. Developers who wrote software at point (1) are now being punished for something they did before the US deemed it to be illegal.
Let's say the speed limit is being decreased. Would it be fair to jail everyone who went over the speed limit in the past, before this decrease was even announced?
The 3 owning accounts of the github tornado cash org were banned or suspended. This is not a legal punishment for a crime, but github covering their own ass legally.
Github banning someone is categorically different from the US government jailing someone. You are conflating two entirely different things.
You seem to have taken the outrage bait that this tweet presented and ran with it without verifying the situation.
There are interesting things to discuss around both the precedent of the sanctions and the ability of large corporations to terminate accounts at will. However the "github is banning people who just contributed to open source and this is wrong because what they did wasn't illegal when they did it" outrage meme is misinformed, confused about how law works, and is generally distracting from all the actually important topics.
1. Developers write open source software
2. Open source software is deployed for money laundering purposes by other people
3. Developers who wrote software at point (1) are now being punished for something they did before the US deemed it to be illegal.
Let's say the speed limit is being decreased. Would it be fair to jail everyone who went over the speed limit in the past, before this decrease was even announced?