Well, the problem with 'good intentions' online is that sometimes they are not taken that way.
It's all in how you approach them with your writing style. Do you put a disclaimer in your reviews? Like for me, I put in this text below:

Here are a few things I noticed while reading. Please remember that these are only my suggestions/opinions and it's ultimately up to you to choose what works best.

With that disclaimer up there, the writer at least knows that whatever I say is not meant to insult them, but to help.

In the meantime, you've done the right thing in trying to explain yourself to the person, and hopefully they will get back to you. Until then, you just have to continue working on how you present your reviews; join groups that rely on reviewing or even go through the reviewing page to see how other top reviewers do it. You can get some inspiration from them.