I also had a bedbug problem last year.
For me, my reaction would depend a lot on the general experience. If the entire stay were horrible, i would definitely write a bad review and demand a compensation.
In my case, the room was wonderful, and the host extremely helpful and overall wonderful, so i just consider the bedbugs an "accident". Very unpleasant one, though. So i first sent a message to the host letting him know. He excused a lot, promised to handle the situation for future guests and offered me to refund the cost of my stay.