Savage Love contained an interesting letter this week talking about motorcycles and the danger inherent in them. The letter writer had a real fear of the danger of motorcycles and was unsure what to do when their committed partner decided to buy one. Dan Savage's advice was bloody terrible - withhold sex until they do what you want - but the comments had some really interesting discussion on the actual safety hazard motorcycles present. This came up in my family because my dad bought a motorcycle when I was in my early teens and I am sure it made my mom nervous; all three of my father's brothers have been in accidents on motorcycles that range from serious to catastrophic.
Certainly motorcycle use is correlated with death and injury. A very large part of that correlation can be accounted for by the fact that people who like to drive fast, refuse to use proper safety gear, and act recklessly tend to buy motorcycles. Even then though a motorcycle is still more dangerous than a car. The problem is that some people use this as sufficient to dismiss any motorcycle rider as a suicidal lunatic. By that logic we should dismiss anyone who uses a personal vehicle instead of public transit as unfit for partnership due to the increased danger. Same goes for people who drink too much, eat crappy food, refuse to exercise, or smoke.
Dangerous activities in a partner should be evaluated with an eye to the actual danger incurred compared to the others dangers we with live with all the time. If your partner wants to head to biker bars, get wasted, and then motorcycle home without a helmet at high speeds you are damn right you should be worried! If, on the other hand, they want to take weekend drives now and then and are paranoid about wearing maximum safety gear and took defensive driving courses, why worry? It would be more dangerous if they developed a taste for sugary treats from Starbucks.
One thing you absolutely should not do is follow Savage's advice. Obviously if one's partner makes it clear that certain things are flat out deal breakers before committing there is an obligation to respect those feelings but withholding affection to force obedience is total garbage. For one it will cause bitterness and resentment and for two the precedent is set that affection is to be used as a weapon of control. That will not end well. If you can't deal with something your partner is doing then be a damn adult. Tell them you don't like it, tell them how much you don't like it, and if it is that important and the two of you cannot reach a compromise (which you damn well should) you leave. If it isn't important enough to consider that then it isn't important enough to wreck your intimate dynamic over either.