Firstly Armaan was invited he did not crash into the party and secondly he didnt want to make a scene,he is saying or doing what he is because he is in a drunken state.Armaan has gone through so much pain and he hasnt let a soul know.He definetely wants to see SR happy together,but it must be painful to live with the fact that the girl he loves the most more then his life isnt his.Whatever he feels atleast he hasnt harmed anyone ever,but sometimes things reach the limit and thats when such a situation arises and if Sid is really a friend and considers Armaan as his brother then he will understand rather then be annoyed or react wrongly.Because if Armaan is his brother then he is too.