Yup.
Would people who think bestiality with a shapeshifting bear be fine with the option to have sex with an adult spellcaster who shapeshift into a child? I think not. We all know that is reprehensible whether it was an option or not.
Your logic falls apart now, right?
You would rightly be outraged by the above scenario's inclusion.... so why is beastility fine but 'child sex' with someone who is actually a grown adult not? Its gross. We all find it gross, and with good reason.
Having sex with a bear is gross. For many reasons. And, it being 'illegal' is number 1million.
But, hey, it's in the game, and a choice. A choice I will never make so its all good. But, just be honest.
fyi, Comparing sex between two consensenting male human (or humanoid) adults or two consenting adults who happen to be of different skin colour to bestiality is homophobic and racist.
Having sex with a guy is not the same as having sex with a bear. I don't know why that's a difficult concept. Animals cannot say yes. Guys who can turn into bears can say yes. Beastiality is having sex with an animal, not having sex with a guy who temporarily looks like an animal.
And to answer your question, it really wouldn't make any ethical difference if the guy shapeshifted into a child either, because he would be no more an actual child than he would be an actual bear. Though of course we might worry a bit about the partner who finds it arousing to have sex with someone who looks child-like. Not because the act of having sex with an adult shapeshifter is wrong, but because we worry said person might also be interested in repeating the fantasy with a non-shapeshifted partner.
That said, you really have to learn to differentiate between what something looks like and what actually is. Suppose a person has a development disorder that hinders their physical development, making them look like they're 13-14 years old even though they're 30. Would such a person also, in your eyes, be strictly banned from having sex, simply because it looks like sex with a minor? How about a minor that looks 20, then? Would that be okay merely because ti doesn't look like sex with a minor?
By the way, do you have any idea how many people your character is likely to kill over the course of a game? Why is it that you're this much of a wreck over a single case of consensual sex but completely disregarding the graphic murder of many, many people? Do you think that is right and proper and not totally sick shit?