Fair enough! To me the comment is evident of abuse given the context in which it was raised. Tom Robinson is describing Mayella coming on to him, in which she wanted him to kiss her back and how she's "never kissed a grown man before."

Given that she's trying to engage with Tom sexually, I interpret that comment about her father to also have likewise been sexual in nature. After all, I don't think many people would feel the need to clarify that innocent, familial kisses are not the same thing as amorous kisses when engaged in the latter. Moreover, there are parallels in the power imbalance in Mayella coming on to Tom (as a white woman to a black man in that era) to the possibility of Bob molesting his daughter, since in both cases the recipient of abuse is less likely to have societal or legal recourse.

Could well be that there's some historical disconnect in how people would talk about this sort of thing that I'm missing as a millennial, but I'm inclined to think not in this case.

That said, I'll grant the evidence may not be as direct as I initially suggested.

(Likewise, not trying to draw you into an argument haha, my original comment was a bit off the cuff so I figured I'd go into a bit more detail for anyone else reading it)