Usually, people consider consensual and non-consensual heterosexual relations as very different, but consensual and non-consensual pedosexual relations as nearly the same.
This comparison shows that statements of the following type are nonsense:
The presence of power difference is not a counterargument. In nearly every adult/adult relation there is also a power difference. Thus, this comparison shows also the nonsense of statements based on a pure existence of a power difference.
Another, more complicate question is the quantity of this power difference. The straight assumption is that this power difference is much greater for adult/child relations than for adult/adult relations. But there are reasonable counterarguments, that this is not always the case. F.e., there is the "blackmail power" of the child to tell about the relation and the power of the "more attractive", not so much interested in the relation, which is also often on the child's side.
Nonetheless, even assuming without questioning the presense of a great power difference, we can compare the pedosexual relation with adult/adult relations in a power context (f.e. boss/subordinate). For such relations, special protection for the subordinate against power misusage by the boss is necessary, but the participation of the subordinate is not irrelevant.
The other main counterargument is the general lack of information of the child. Here it is also reasonable to ask if there is really a lack of information about sex for a typical say 12-year-old. But, in general, this counterargument describes the boundary of this comparison.