The question is pretty "nuts". Take a look at what is actually being erected and why.
Beltane has no connection of any sort (apart from recently invented ones) with Baal.
Why are they rebuilding The temple Baal in Trafalgar Square? Wasn't Baal the god of Child sacrifice and isn't England a Christian country? This event is closely followed by Beltane, Baals festival.
Why should they not? After all, England abounds with temples to the Flying Spaghetti Monster (they're called trattorias) and nobody complains. We Pastafarians are a tolerant lot.
R'amen.
Baal was not any single one God, Baal is a title meaning lord it is mistakenly seen to most christians as a single god. At one point in history even the biblical God was known a Baal Yahweh. Married women often referred to their husbands a Baal. The rebuilding of an ancient temple is a historical venture. England is more a secular country now days. It's church attendance is declining immensely.