An absolutely vast amount of hospitality goes on in Parliament- MPs having receptions for charities, major local employers etc. Very little of it is MPs getting pissed by themselves or with each other. Other roles that involve relationships and networking are similar- big companies, law firms etc often have in-house hospitality services, including alcohol.
If they didn't have bars on the Parliamentary estate, they'd all be fighting to book out the nearest ones in Westminster (which London office workers wouldn't thank them for) and it would be a security nightmare too.
So I do think it's a deeply unserious idea- and a sign that the MP concerned arrived in Parliament without a good understanding of the range of activities MPs undertake.
If people are drinking excessively- and especially if they're then behaving badly afterwards- that's an obviously different point. Fortunately there's now a well-established independent complaint scheme in place to drive out unacceptable behaviour.