Was anyone shocked about the part in the seventh Harry Potter book when Lupin wanted to join their team?

Yes it was completely shocking and so unlike Lupin! I think Lupin was really stressed about having a potential werewolf baby, he felt guilty, as you would. He wanted to do something reckless and get away. Even though Harry could have come across as a bit mean to Lupin, he definitely did the right thing by telling Lupin to go home to his family. Of course he is in love with Tonks and would be incredibly happy if he weren't a werewolf, he feels, again, guilty because werewolves don't normally do that kind of thing and he was breaking many rules. It was just a really unlikely case and I think Lupin was super stressed. There's my views.