They are leaving you alone. Noone is forcing you to use instagram. If instagram wants to be a safe place for their chosen audience, that is their choice.
It's a photo sharing service, for chrissakes. Not a debating forum central to the survival of democracy. Not a bullying-deathmatch server. Not your soapbox.
If you don't like it, find or make one that does what you want.
Your freedom of speech grants you the right to post what you like on _your_ site.
Noone else is obliged to host your whiny rants, listen to them, respect them, or respect you.