Re-enacting trauma

It is mentioned that people traumatized in the past "want to go through the same situation but that it not result negatively as it did in the past". That's why, for example seek humiliation in their sexual practices. This quoted sentence however does not explain the sexual arousal that masochist experience. They may be humiliated by their mistress and enduring that and going out 'alive' would be enough. But why erection? Well, it is because that quoted sentence is half true, as for sexual practices. The masochists' goal is not to simply to endure the pain again, but to focus on neutral sexual stimuli, eg their mistress body, her power over him, etc and have erection despite the pain, humiliation, etc. They need to alleviate themselves from the inhibitory effect of their past trauma towards their sexuality. This way they can achieve erection. Ofcourse that erection is not greater than the erection of a healthy sexual man with free mind from sexual inhibitions (or at least well absorbed and defined sexual inhibitions and not exagerrated ones etc). It is just greater erection than their erection they have under their inhibitions.