Why so much hate?

Hey! I’m a mainlander based in South India. I see the posts in this sub regularly and I can help but notice why this sub is so against Bangladeshis? I mean I understand that their culture is very different from northeast India and also there’s a lot of illegal immigration going on which is changing the demography. But why the casual racism, calling them dogs or kanglu and other such things? Many northeasterners already are experiencing racism against them but why become the perpetrators? No hate, just curious