同意或者反对

I agree with you.

我同意你说的。（*简单的）

Building on what XX has just said, ....

就刚才XXX说的，...

I am with you..., but [main point].

我明白你的意思，不过... （这里I am with you不一定表示同意也不一定表示反对，它主要的意思是说"你说的我听懂了/我跟上你说的了）

I follow your logic, but have you thought about/considered this... [main point]...?

你说的我明白了，但是你有没有想过...（和上面一句话的逻辑是一样的）

I see what you are saying, but I'm not sure I would argue that...

我明白你的意思，不过我不确定我的观点与你一致... （和上面两句话的逻辑一样）

With all due respect, I think...

恕我直言，我认为...