@Rebecca160 You might also say that you felt uncomfortable with the guest in your home, and that you found it difficult to communicate easily with him. The facts, but without judgment. The one phrase that all experienced hosts will recognize is 'This guest is better suited to a hotel environment'. This alerts us to the fact that we likely would not want to host this guest.
Unfortunately, Airbnb's current review system favors guests at the expense of hosts. Guests are given far too much power over the success or failure of a given listing - Even one low-star review (often undeserved) can be lethal if the host can not get it removed. And so some hosts understandably become hesitant to call guests out on poor behavior or do not assertively intervene when the guests are breaking house rules due to fears of a retaliatory review; they also fear reviewing the guest honestly because they don't want to look 'bad' to prospective guests or get a raging public response from the guest on their honest review, and so we have many, many reviews that mean very little, which ultimately does not serve anyone in the community.
I have had several guests that had rave reviews and after I saw my Cottage (and the hot tub) when they left I knew this could not have possibly been true. I just don't believe that a person with 5 Star ratings across the board for being Clean and following rules suddenly turns into a house-rule breaking sloth the minute they enter my rental.
I give honest reviews now no matter what, because I decided the only way I can both survive and thrive emotionally as an Airbnb host was to not let fear control my actions in any way, ever. Not always easy, but possible, and it is working well for me so far.