おっしゃることはよくわかります。
Ossharu koto wa yoku wakarimasu.
I certainly appreciate what you’re saying.

Even if a client or customer has taken an utterly unreasonable position, you have to state your opposition in a way that minimizes the possibility of exacerbating the situation. One way of doing this is to start out by clearly acknowledging the other person’s point of view:

おっしゃることはよくわかります。
Ossharu koto wa yoku wakarimasu.
I certainly appreciate what you’re saying.

お気持ちはよくわかります。
Okimochi wa yoku wakarimasu.
I definitely understand how you feel.

たしかにその通りだと存じます。
Tashika ni sono toori da to zonjimasu.
Without a doubt, it’s just as you’ve said.

なるほどお客様のおっしゃることはごもっともです。
Naruhodo okyaku-sama no ossharu koto wa gomottomo desu.
The situation is indeed just exactly as you’ve described it.

Whether or not you actually consider the other party’s viewpoint valid is an entirely different matter, of course, and one best kept private. The idea is to open with an ingratiating stroke aimed at putting the listener in a mood to entertain a different point of view. Pulling off a graceful transition into the latter is the second part of this one-two approach:

おっしゃることはよくわかります。ただ、私どもといたしましては ……
Ossharu koto wa yoku wakarimasu. Tada, watakushi-domo to itashimashite wa …
I certainly appreciate what you’re saying. It’s just that, speaking from our point of view …

お気持ちはよくわかります。たしかにそういう見方もございますが ……
Okimochi wa yoku wakarimasu. Tashika ni souiu mikata mo gozai-masu ga …
I definitely understand how you feel. That’s certainly one valid way to look at the situation, but …

たしかにその通りだと存じます。ただ、こういう見方もあるのではないでしょうか。
Tashika ni sono toori da to zonjimasu. Tada, kouiu mikata mo aru no de wa nai deshou ka.
Without a doubt, it’s just as you’ve said. Only, I wonder whether it might not also be possible to look at it this way: …

なるほどお客様のおっしゃることはごもっともです。しかし、このようにさせていただけばもっとご満足いただけるのではないでしょうか。
Naruhodo okyaku-sama no ossharu koto wa gomottomo desu. Shikashi, kono you ni sasete itadakeba motto gomanzoku itadakeru no de wa nai deshou ka.
The situation is indeed just exactly as you’ve described it. And yet, it seems to me perhaps you might be even happier in the end if we were to handle it this way: …

If there’s a hint of flattery in your approach, all the better to prepare the way for your own position, the essence of which is to make what’s already good even better. The thing to remember is, you can avoid giving needless offense by withholding your own views until you’ve first paid the obligatory tribute to the other person’s ideas. Then, when you finally get around to your opinion, you can more or less casually mention your doubts or dissent. Here’s one more example:

お話を伺って大変勉強になりました。基本的には賛成ですが、二三、感じたことをお話ししてよろしいでしょうか。
Ohanashi o ukagatte taihen benkyou ni narimashita. Kihon-teki ni wa sansei desu ga, ni-san, kanjita koto o ohanashi shite yoroshii deshou ka.
What you’ve said is very enlightening. Basically, I agree with you, but there are just a couple of things I’d like to talk over, if I might.

– Source: A handbook of common Japanese phrases –