No matter where I go, how many people I help and how many bandits and monsters I kill, everyone hates me to the point there even nasty to me :)

Was wondering does bumping into people while running or on Roach have an effect on the people within the game?

No, they hate you because you're a witcher. :)

Don't fret though, you'll be graced with more than enough love on the road as well.

I found the only nice people are the ones you do quests for, and (usually) the people who fill in the settlements that you clear out. Everyone else makes you feel like you're trapped in the comments section of youtube or something equally awful.

In the universe of the Witcher, the witchers are looked down upon or even hated. They are seen as mutants and freaks. But the people still need them to kill monsters :)

People cursing and the one that got me for a second was some woman screaming and running away.
Immediately looked around for a baddie then figured she was running from Geralt:-)

Geralt has such an undeserved bad rap. Who would think people would despise someone who walks freely into their homes, sporting two massive swords, and happily helps himself to all their belongings. The nerve of these people, sheesh! :)

That's a world Sapkowski has created and CDPR made virtual, where in some places is basically quite discomforting to be.
But walking through settlement where you helped people and hearing things like "If I got a son, I'll name him Geralt" is much more comforting.

Not all Witcher's are as reasonable as Geralt and Vesemir.

The cat school of witchers essentially turned into a cabal of mutated assassins, and members of the Serpent school (namely Letho) went around killing kings and nobles. Hence why the last game was called 'Assassin of Kings'

So, yeah...considering the Northern kingdoms got the worst of it, it's not hard to see why they have prejudice.

There was basically propaganda used against Witchers and it took. It's possible to even find these books in the world. Monstrum - A Portrayal of Witchers. They claim all kinds of ridiculous falsehoods, but the simply peasantry ate it up. Witchers themselves don't really do PR. Geralt doesn't even try to counter most of the nonsense he is confronted with, because it's a waste of time.
It's the same for sorceresses. Everyone calls them by derogatory terms, where witches is still one of the nicest. For far too many people it seems to be easier to just assume the worst of everyone else.