schlong, if it's not your thing it's not your thing...that's absolutely fine. Not everyone is into kink and there's nothing wrong with that at all.
It would certainly be abusive if it were being done to someone who didn't want it or consent to it. For someone who finds the restraint and roughness exciting, it can be part of very satisfying play. Gagging gives me a sense of helplessness which heightens my submissive feeling and trust in my dom. It also intensifies my orgasm; I can't express it through crying out, and so it gets turned inwards and becomes harder. Hair pulling doesn't do anything for me personally, but it does for many others.
It's not abuse when it's consensual and to mutual benefit.
A further thought on the 'control' thing...to me, it means in part that I can't 'manipulate' my dom in any way (topping from the bottom, something I have been known to manage with people who weren't the right fit for me, some of whom I don't believe were true doms). Suppose there is a certain way I'd like the scene to go. I can't control what my dom does; he won't be swayed by my big eyes or sweet talk or attempts at persuasion. He might, if I ask openly, agree to it, but it's still his decision, not mine.
If he decides he wants to do something else, I still consent to and submit to his will. But if he does something that is against my limits, or which I realise I absolutely genuinely do not want on any level, I do have the power to safeword and stop it. That's not manipulation, but it is an exercise in ultimate control. Or as one dominant told me once: "I set the scene, you set the limits. I say what does happen, you say what doesn't."
Also, aftercare. You don't have to be in a committed relationship or madly in love with your dom, but there should definitely be aftercare. You may feel fragile or vulnerable after a scene but you should not feel broken or damaged. Ideally, you should feel high.
Offred's right that a safeword alone isn't really enough; you do have to know each other and be on the right wavelength with each other. I love BDSM but I do accept it comes with risks and I have been unfortunate enough to have had one or two bad scenes when my dominant wasn't paying proper attention. He subsequently apologised and we worked through it, but dang, I never knew a bad scene could have an effect like that...and it took some time to get over it. There are still things I don't like to do as a result of it.