That is YOUR opinion. You're opinion on relationships is not law. End of story. Nothing you say, believe or feel, can dictate how another person feels or believes. Just because someone might have a conflicting belief or way of showing affection does not mean it is any less valid. There ARE people who show affection by causing pain. They are called SADISTS (wow there is ACTUALLY A WORD FOR IT), granted they are usually coupled with a masochist, but hey! THEY EXIST. Those who derive pleasure from the giving and receiving of pain and humiliation, in an endearing and healthy relationship. Your word and views are not law. The world is a big place and there are countless ways to show affection, and despite your belief, causing pain and humiliation is indeed one of them.
Also, Haibara's personality type is not the issue here, nor does it have anything to do with the issue at hand. Being stoic has nothing to do with how one acts in a relationship, only with how they deal with emotions (and Haibara doesn't even FIT entirely into that category, she is not DEVOID of those emotions she CHOOSES not to show them, she isn't indifferent, and she allows herself to feel emotions at certain times, which CONFLICTS with the philosophy of stoicism)
And friendship is a choice, and friends come and go all the time. The span of time in which Haibara has known Conan is NOT enough time to consider their friendship committed. Neither is Ayumi for that matter. At this stage, I'd hesitate to say whether any of the three have any real feelings of interest between each other outside of INFATUATION. (They have all known each other for LESS than a year). As much as I shipped the pairing of ShinShi, I'm really getting tired of those debates, hence I stopped participating. I'm letting Gosho tell it (though he seems to be failing at that too since he cannot even complete the damned emotional arc of the characters after the London Case).
PS: I'm not saying that Haibara is a sadist, I'm just stating that there are many ways to show affection and that happens to be one of them.
PS #2: No matter what is posted after me I'm not posting again. This is going no where fast and I don't want to waste any more time on another pointless debate. I have more important things to attend to than a debate on relationships, and their implications in a fictional world.