Guys , I have been asked to fucking merge two bootstrap themes together. Why does my lead think that's a good idea ? I mean they are complete themes for a reason and both have their own custom css. I have been busting my ass for the last two days to make it work.I fucking hate css now.

No, css is not evil, that God forsaken mother fucking useless piece of horse shit wanking ass fucking whore framework known as bootstrap is.

What a nightmare that's going to be! Rewrite the fucker from scratch with the styling and behaviour you want.

Show the teamleader a diff from two complete css files and two him that you are not sure which of them you should keep and which to drop. Finding this by trial&error will take longer than creating something new basing on those two. Then sit with him and discuss what 'visually' to keep and what to drop.

That's what I would do. For me it's a least passive aggressive solution that shows the teamleader his mistake.