Yeah, but the comment OP is responding to was explicitly about letting kids "explore their sexuality".
Emphasis mine. The comment is not, in fact, about letting children explore their sexuality, but people. (When you consider the parent of that comment, that still does not add context implying that we're talking about kids.)
The only part of the comment which discusses children is this:
> For the last several decades society put massive pressure on kids to conform to heteronormativity.
To read this as sexualizing children is misunderstanding the term heteronormativity, but regardless, this is the behavior that is being criticized, not championed.
> For the last several decades society put massive pressure on kids to conform to heteronormativity. With these pressures lessening more and more people are feeling empowered to explore their sexuality.
In a maximally generous interpretation, you could say that the "kids" in the first half and the "people" in the second half of the statement are completely different subjects. I think that is a bit of a stretch, though.
"For years I have been pruning the tomato plants in my garden. Now, I just let the _plants_ grow".
Anyone reading that would assume "plants" refers to the aforementioned tomato plants, not cucumbers.
Consider that, in the example sentence you came up with, you are referring to the same subject, at different times.
Also I'm not accusing anyone of pushing this on their kids, rather, our society does it in massive doses. Watch most children's TV shows or movies and heteronormativity is abundant.
For a pretty clean example of this check out the movie Up by Pixar. The first 10 minutes of the movie are devoted to Carl & Ellie's relationship and the loss of that relationship serves as a major driver for the movie.
Also there's nothing wrong with showing children this kind of content. It helps them make sense of the world. However, there is an issue with representation. When it's all they see then it constrains their minds as to what is possible.