It's fine to feel uncomfortable about something or to personally dislike something - the important thing is just that you don't judge those who do enjoy it.
I think the important thing to remember is that s&m is generally pretty much entirely consensual - just like tugs. Because there's so much scope for things to go wrong, people involved in s&m activities will generally discuss their preferences, what they're comfortable with and what they're not comfortable with in great detail in advance. So even if within a scenario, it doesn't seem like someone is giving consent or that the dom is just improvising what to do without checking it with their sub first, chances are it's already been okayed outside of the situation. Also remember that consent doesn't necessarily mean saying, "You are allowed to do this specific thing to me" - it can also be a case of merely saying "I want you to do whatever you want". Just like in bondage, where subs sometimes actively don't like to have any say in what happens to them, subs involved in s&m will feel the same way. It probably just seems non-consensual to you because you probably don't understand why people enjoy being in pain (which is fair enough - I can't say I really understand it either). But from what I can tell, the more hardcore the activity, the more likely it is that the people taking part will be incredibly careful about setting out their boundaries beforehand.
Obviously if consent blatantly hasn't been provided in the situation and the sub isn't happy about it, then you have every right to feel disturbed and upset about it. But no more disturbed and upset than you should feel if you were to hear about a standard bondage situation in which consent wasn't given and the sub clearly isn't happy about it.
Basically, just try to keep an open mind. It's fine to not like something and know that it's not something you would want to engage in - but at the end of the day, a fetish is a fetish and people don't exactly choose to have them, so it's important not to judge people simply because it's something that they DO enjoy. Maybe try talking to someone who is into it who would be able to explain why they enjoy it? I'm sure there are plenty of people on this board, and having more direct contact would help you to understand it a little more. And if you just can't get your head around it then that's fine too - just avoid commenting on it, to make sure that you don't upset or offend anyone
