If Starmer suggested taxing football income you would be being a bit daft if you claimed that it was going to hurt the guy you just replied to on the grounds that he earned fifty quid from football.
“But he’s a worker too and he’s not rich and you promised not to tax him” is sillier than saying that he isn’t covered by the promise to not raise taxes on working people.
That’s because (and this is the bit that’s not quite got through to you somehow yet) the vast, vast, vast majority of his income is from working, not from football.