Someone from the US may correct me, but here's my understanding. Baseball is played with a hard ball; people playing it can get hurt. Children start by playing a similar game with different equipment; one of the differences is that the ball is soft - I think it's bigger too, but you'd have to check that. At some stage, people start expecting adolescents to play the more demanding and dangerous game. When you play hardball, idiomatically, you start behaving in a more demanding (and potentially hostile) way. I believe this is a US idiom; there is a close equivalent in Br English - 'the gloves are off' (a reference to bare-knuckle boxing).
When you take a first-hand look at something you go and see it for yourself, rather than rely on eye-witnesses(who would provide second-hand reports.