@Mike36
I think it's likely to be an 'inquiry' rather than a booking 'request' if it is a kind of spam message.
Although on the app it does state 'accept' or 'decline' - however drill down further and the options are 'Send special offer', 'pre-approve' or 'decline'
As it is an inquiry there is no need to press on any of these option buttons , you should just answer the inquiry to keep your response rate high and fast, even if you answer only with a simple full stop.
It won't have any bearing on your profile or superhost status.
You can press the 'report this user' flag at their profile if you feel it's intrusive.
I think there is a cap of ten messages a profile can send out to individual hosts before they are suspended as an airbnb feature to stop mass spam messaging.