Just because you can sing it over it doesn't mean that it's copying it. I can sing the hook of 'Heartbreaker' over virtually anything, does
that mean it's copying every song? Many songs follow a typical chord structure which means that they can often be "mashed together". This is
especially true with songs that contain loops, such as 'Touch My Body' or 'We Belong Together'.
Truth is I don't think 'WBT' and 'TMB' are similar in anything other than tempo. 'WBT' is a very simple song, with one vocal
through the whole thing, where as 'TMB' has a lot of layers. 'TMB' has a more diverse structure, too with a pre-chorus and bridge.
'WBT' has neither of those.
Also, 'WBT' is sung in a very low register througout, and then octaved up for the belting finale. 'TMB' doesn't do that... They're
pretty different to me. Mariah didn't follow 'WBT's formula at all, I think songs like 'Thanx For Nothing' will do that, though.