Equally people can raise a safeguarding risk to children of religious people inappropriately inputting to SRE.
I know posters on this board are most comfortable focusing on the risks of transition, but there are a whole load of other safeguarding risks out there. Teenage girls being raped and sexually abused by boys in their schools. Boys getting warped by porn to think coercive sexual behaviour is normal. Gay children being made to feel strange and different, affecting their mental health.
Conservative and religious groups often want to shut down SRE to purely discussing the mechanics of sex in science classes, and all the "relationship" stuff to be dealt with by parents. That opens teenagers up to loads of risks, even more so now than ever before when their alternative source of information is the Internet.
Many children don't have parents who are equipped to inform them about healthy relationships and sex, for a whole multitude of reasons. So I think an attitude that relies on "parents know best" is paradoxically a safeguarding risk.