They only block really antagonistic regimes which don’t comply with UN and other international sanctions. It has to be a really rogue regime that threatens regional or world peace.
If current conditions are not a good predictor for future conditions, isn't it equally likely that other countries (same as the US), could change in the future to sanction other countries and restrict online services operated there?
On the other hand, blocking Iranian GitHub accounts is helping to change Iran regime? Are Iranian GitHub Users developing nuclear bombs there?