Mary Berry doesn't therefore you must be banned from doing so

It's said that people become more conservative as they grow older - that liberal mugged by reality thing. It is perhaps possible to become too illiberal as this process happens:

Sugary drinks should be banned, Mary Berry has said, as she revealed that she refuses to give her grandchildren anything other than water to drink.
....
“I honestly think there shouldn’t be sugared drinks. All my grandchildren drink water all through the day. I’ve just had them to stay and at breakfast they have water. They don’t even know what sugary drinks are.”

How Mary Berry grandmothers her brood is of course up to Mary Berry. That's rather the point of being liberal. It's also fine that Ms. Berry urge others to do as she does. That's also that liberal free speech thing.

However, Ms. Berry does not boogie the night away therefore no one else should? Not that we know either way but Ms. Berry does not attempt legovers with interesting people she is not married to? Therefore the law should be changed so that none may? May Berry has only soup for lunch, as she tells us, therefore soup should be the only lunch for all Britons?

To examine the logic is to see how ludicrous it is if we are to maintain any pretence at all of being a free and liberal society. Our aim, in so far as there is an aim to governance at all, is to maximise the amount of what people desire to do, as defined by those people themselves. If that includes sugary drinks, bopping 'till they drop or the fruits of the sexual revolution well, that's just up to them.

It may be that Ms. Berry is only urging that parents and grandparents ban sugary drinks for their own brood(s). But there are very definitely others out there who would ban them for all.

There's a remarkably large number of things that distinguished ladies of a certain age do not do but which many others do and enjoy doing. Our actual ruling principle is and should be chacun a son gout.