You dont lose basic humanity when you become a Witcher
No, you only lose it if you're a normal human, apparently.
What the fuck are you even talking about, humans in this game are pretty fucking human. Some are cowards, some are brave, some are good, some are evil, some are trustworthy, some will lie to you, there are simpletons and sorcerers, kings and bandits, some are living one day at a time and some have schemes reaching years into the future. Some are interesting, some are boring, but most of them are pretty real. The game portrays them both as absolute filth and paragons of good and that's basically definition of human.