I'm sorry, but i do not think that the gentleman was inclined to agree and discuss. In fact i think he found a thousand excuses to go away:
1) the shower was not dirty, not moldy : simply the silicone was blackened and we have already provided;
2) he said that he found a hair on the ground, but did not say that he presented himself with two dangerous dogs ( greeted with my usual kindness) that would leave a sea of hairs on the ground at the end of the stay : ungrateful!!!;
3) the stains on the sofà were just the type of sofà ( i still put a cover to avoid excuses and speculations like these);
4) he said the the oven was dirty : FAKE, it's old, but not dirty : ....but we provided a new one to avoid pretexts and speculations like these;
5)just arrived he started taking pictures and sending them to Airbnb . If, as you say, you could solve it, you would not have used this behavior.
I repeat i think that there were all excuses to get the repayment from Airbnb and go the other way he already in mind.
It is first time who happened this thing , after that i have had many, many guests in my house, withouth they say nothing bad on my house!!!
And here i end the story, i would have other things to emphasize, but.....the guest is sacred!!!
For me there are many very positive reviews, the maxim vote 4,8/ 5 and my profile of Superhost for 2 years.
A very warm greeting to the real and sincere travellers of Airbnb.