It's not cool 是不酷的意思吗？你要真这么认为，那可就尴尬了~
It's not cool！
I do not agree with this. "Cool" is a popular way of saying "OK" in the U.S. 意指我不同意这个想法或做法，cool在美式英语中是OK的流行表达。
-I got a plan. It might get us both killed, but, if it works, it will be a totally boss story. Cool? 我有一个计划。可能会让我们俩都丧命，不过如果成功，那绝对会是个传奇。可以吗？
- No, no, it's not cool. Cool? No, I said it's not cool. 不，不，不可以。可以吗？不，我说了不可以。
◆我不同意的其他说法◆
"That's quite true, but…"
貌似是这样的，但是....（外国人说话委婉，重点都在but后面了）
That's quite true, but on the other hand, we have to think of our priorities.
那很有道理，但我们还必须分清轻重缓急。
(I'm afraid) I cannot share your opinion.
我恐怕不能同意你了。
(I'm afraid) I cannot share your opinion, but it's understandable for you to think so.
我不同意你的观点，但你这么想倒是可以理解。
I don't think much of that.
这个我不太赞成。"think much of"表积极态度：重视，尊重、赞成
I don't think much of his idea.
我觉得他的主意并不高明。
I wouldn't look at it like that.
我不会用这个角度来看。"look at" 有“看待问题”的意思； 每一件事都有两面。There are two sides of a story. 而对于同一件事的看法，每个人或许都不尽相同。