Bertrand Russell was for a while a brilliant mathematician. And like many mathematicians, he also thought he was a "philosopher".
His arguments "against Christianity" are about as insightful as any others he had in lifetime outside of mathematics.
Actually this is incorrect; Russel absolutely was a philosopher:
Bertrand Arthur William Russell (b.1872 – d.1970) was a British philosopher, logician, essayist and social critic best known for his work in mathematical logic and analytic philosophy.
His philosophy was of the logical empiricist/logical positivist/ Humean variety (he was a prominent member of the so-called Vienna School of Logical Positivism which flourished in the early 20th century until its demise), but a philosopher he was, and I would say he was a pretty good one for his time despite disagreeing with very many of his opinions, philosophical, social, moral, and otherwise. Today Logical Positivism is essentially dead (killed by Godel's Theorem and the set-theoretical paradoxes Russell himself discovered while developing his own system, after which Russell's ten year project with Alfred North Whitehead, Principia Mathematica
, which sought to reduce symbolic logic to pure mathematics and set Logical Positivism on the firmest foundationalist grounds, was simply discarded unpublished in the trash-heap of history's wrong starts by Russell and Whitehead themselves) -has been supplanted by the successors of Popper's Falsificationism, Kuhn's Paradigmatic Revolutions, and varieties of Postmodern denials of reason (e.g. Feyerebend, et all) to name but three important trajectories. Russell's History of Philosophy
, which I own and have read, was actually cited as contributing to the decision to award him the Nobel Prize for literature in 1950. Whatever my disagreements with many of his conclusions, the man was if nothing else a philosopher, and in my book an amazing writer and thinker, though in my view he was wrong about God and Christianity (albeit not necessarily wrong in his critique of some of the rationalist proofs of these which he critiqued -cf. his debate with the brilliant Catholic philosopher Frederick Copleston, whose multivolume A History of Philosophy
I regard as much better than Russell's simply because it is so much longer and detailed).
As a man, Paul Johnson described Russel as pretty deplorable, even despicable, in his personal life (Paul Johnson, Intellectuals
, chapter 8: "Bertrand Russell: A Case of Logical Fiddlesticks"). But please don't disparage him for not being a philosopher.
I'm all for critiquing his critique of Christianity -I do so myself- but I think we should give the man his due where his due is deserved.