People also see nature as art. A photo from a butterfly, a cat doing cute stuff, the sunset, and so on. None of them are man made, no one suffered for them to exist (usually). None of these are valid?
Not sure what you mean by "valid" but I don't think anyone's arguing that butterflies, cats, and sunsets are not valid. I love watching or looking at all of them but that doesn't make them art. Again, I think the comment is arguing that the definition of art lies in who created it and why. Not whether it is nice to look at.
Nature is beautiful but it's not art. A photo of nature may be art though.