Remus knew as he was writing his message to the town that Sirius was going to be very against it. At least, the latter half when he consented to the idea of drastic measures regarding his life needing to be taken. It was a terrible cost, and a price no one should have to pay. But at the same time, Remus couldn't put his life above anyone else's. And if he came back from the full moon to realize he'd actually killed someone? Remus would never recover from that.
It wasn't as though he had a death wish. He hadn't said for anyone to kill him on sight. It was just.. a last resort.
Of course he knew Sirius would have a reaction about it. That was why he'd written it while he was at the library and not at home. A little cowardly, perhaps, but Sirius would've probably taken his device and thrown it if he'd seen what he was writing before he sent it to the township. The response he'd gotten overall had surprised Remus a little. No one was shunning him for being a werewolf; they were more just asking what they could do. That part was a bit more promising. The response Sirius gave came as no surprise, however.
It was the first time he'd been on the receiving end of his anger in this world, but certainly not from his own timeline. Sirius yelled at him plenty before the end of the war. Every time it broke Remus' heart a little more. And wasn't this more of the same? Remus was acting in a way he thought was best to keep Sirius safe. The context was different, but the result was still the same. Sirius was yelling at him, hurt and upset and Remus completely understood. He wasn't going to fight him about his feelings. He wasn't going to fight him at all.
He left the library, tattered shoulder bag slung over him and set off for their home. Remus had left things in order for the next few days, as he didn't intend to go back until after the full moon. He was going to start falling ill soon and he needed to prepare for that, as Sirius was already in bad shape and Remus did not want him or James having to step in to take care of him this time around.
Remus arrived home, hung up his bag and shut the door. Naturally, he went right to where Sirius was and sat beside where he was lying down. Without hesitation, he started to stroke and pet his hair, just as he'd been asked to do. "You can shout, if you need to. It's all right."