Sexual Harrassment, Where do we draw the line? Options

[Tsukuyomi-No-Mok...]

Before i post this I would just like to say that i'm a bit angry because of some ish i had to deal with last night and today relating to this but anyway here goes.

So my question is when a girl calls for sexual harassment i think there needs to be a line drawn as wo what exactly that is because if a simple touch or tap or poke is called sexual harassment even if it's accidental the person who did it is basically screwed.

What happened with me last night was i went to pick up my phone that i dropped behind a bench that people were sitting on and i bump in to this girl accidentally and my hand barley touches her ass and i pick up my phone and jus walk away.
next thing i kno i got this girl yellin in my face and she grabs my shirt and takes my shades and throws them. I simply grab her wrist to stop her from swingin around and then her sister comes outta no where and pushes me away from her yellin in my face callin me this that and the third yellin and tryna provoke me to do somethin.

so the whole thing goes on for about a good 30 minutes and i had already apologized like 4 times and the girl runs off and gets her boyfriend and what not and tries o fight me but i leave after my people came and broke it al lup.

today some kids knock on my door run up in my room rolin at least 7 deep on me and start gettin at me with this whole i hit girls and i sexually harrass girls and stuff like that and then tell me that they talked to the dean of the school and now the cops are gettin involved and i'm already basically screwed for goin to school cause i have a 5% chance that of beating this whole thing

i'm still tryna figure out how is it sexual harassment if someone touches someone i mean when u say sexual i think that it'd be on the lines of rape or talkin down bout someone sexually or anything like that but simple and pointless things like tappin someone and all that
i mean it doesn't take a genius to know that if u touch someone it's not like it killed you and usually people jus say sexual harassment they can call it on the stupidest things like so a guy touched a girls lower back as he passed by her simply to give her a lil push to get the point that he's tryna move past her. she turns around and says he sexually harassed her by touching her inappropriately. i don't think that's reasonable honestly.

but yeah i've seen it happen so question?
when do we draw a line as to what sexual harasment is and isn't.