I agree that European lenders went overboard, but I can't blame them for requiring strict measures after the corrupt government of one member state threatened the economic stability of the entire EU bloc.
Years of government mismanagement and fraudulent reports had put Greece in a state where nobody reputable would lend them money, in extreme debt, and without an economy to recover by itself any time soon.
Greece could've decided not to take up the bailouts, of course. All austerity packages were passed by the democratically elected Greek parliament.
The EU would've liked Greece to magically go out of debt, but it's not like they were just going to hand the Greek government hundreds of billions of gifts and a pat on the back with a quick "try not to go bankrupt again, OK?". If you lend someone money, you want some kind of guarantee that you're going to get it back. The EU wasn't being evil, it was watching its own back while the worldwide economy took a hit. They weren't alone either; the IMF also demanded reforms to ensure their loans got paid back down the line.
At every step along the way, the Greek government was involved, including causing the instability in the first place. There are plenty of evil things the EU and its many bodies do, but this wasn't a good example.