I would usually be enraged close to the point of violence. I hate other people's saliva. It makes me sick.
However if it were someone I fancied, it wouldn't matter as much. I might even find it hot.
This is because of the behavioral immune system. Sadly to my knowledge the behvaioural immune system is not well studied. I had to observe things and come up with the theory on my own although I imagine that somewhere out there people have made the same observations, it merely hasn't reached mainstream yet because of the subject area it covers.
I have made some observations that may link some cases of pedophilia to anomalies in the behavioral immune system particularly where it is dialed up or less able to dial down in the presence of a potential mate. I suspect there have been constant battles between the behavioural immune system, survival and diseases which has likely left its mark through evolution. I also strongly suspect that the behavioural immune system is adaptive to various circumstances over time such as mate availability and has both a heavy nature and nurture component.
The fact that you have asked this question suggests that you have cottoned on to the curiosity of the behavioural immune system and the circumstances that cause it to radically fluctuate.