From what I've read, people who support alternative lifestyles (e.g. the homosexual/transgender cause) usually make consent a criterion to distinguish acceptable from unacceptable activities. We could examine that from various angles, but let's consider the issue of consistency.
In my observation, the same kinds of people who support the homosexual/transgender movement oppose smokers. Yet tobacco smoking is a consensual activity. More generally, you have the food Nazis.
Perhaps they'd say that's different because that involves dangerous consensual activity. So they'd add another criterion.
Problem is, they defend homosexual activity, which is dangerous. Consider all the health-risks associated with homosexual activity, viz. AIDS, STDs, colon cancer, colectomies. Believe it or not, anal sex, rimming, fisting, scat, &c. just isn't very healthy. Who knew? In fact, bloodletting parties are the chic new thing in S&M circles:
Likewise, it's my impression that the same kinds of people who support the homosexual/transgender movement oppose high school football because they think it's hazardous (i.e. risk of brain damage, spinal cord injury). Yet that's a consensual activity.
Perhaps they'd say that involves minors, so we have a right to tell minors what to do. Yet these are the same people who ridicule abstinence-only programs as unrealistic. Teenagers are going to have sex anyway, so might as well supply them with free contraceptives (and abortion access). But, of course, teenagers are going to practice unsafe sex, too.
What it comes down to is that people who support alternative lifestyles don't begin with criteria, then determine what alternatives lifestyles are acceptable according to their criteria. Rather, they begin with whatever lifestyle liberal opinion-makers champion at the moment, then determine the criteria according to the lifestyle.
For instance, there's a push to mainstream pedophilia.
Of course, once pedophilia is reclassified as just another "sexual orientation," you can guess what the next step will be. The age of consent will be revisited.