Not sure what the fuss is about to be honest.
In a literal sense, and even though it's banter, they HAVE tried to 'Tap up' each other by trying to get either one to join the other at their respective club.
The headline has sensationalised this to act as Clickbait, as the number or clicks increases the revenue from advertising that is on their pages. This is all it is, nothing more. To be fair, they have even used inverted commas around the term to suggest it isn't quite as literal as some have taken it.
This is the problem with internet based "journalism". The only way they can make money online is via subscriptions or advertisement, which presumably is paid based on the number of clicks or views a page has.
I doubt their hard copy would have that headline because there is less need to sensationalise it. In most cases the paper will already have been paid for, and therefore there is no need to resort to clickbait tactics.
Rag fans feel as though the MEN is biased against them also, and without wanting to start trawling through the United section of the MEN site, I'm sure you'd see plenty of examples where click bait is used.
In the cold hard light of day it matters not one jot does it really.