There are several strands to unpick in this useful article. The first is obvious: science is, properly speaking, not about belief but merely about ever-more-adequate descriptions that lead to accurate predictions of previously unobserved phenomenon.
The second strand is that quantum mechanics is merely a mathematical framework that is highly useful, but which clearly doesn't correspond to the way in which our brains have evolved to deal with obvious large-scale physical phenomenon. This has led a great many physicists into absurd speculation that they really should have known to avoid.
The third strand is that the multiverse and quantum theory aren't necessarily connected at all. Eternal inflation, while relying on the notion of quantum tunneling, does not presuppose the nonsense of "every time a choice can be made, the universe splits to accommodate both." Nevertheless, while eternal inflation is a pleasing conceit there is presently no way to test it and therefore it is nothing more than a hypothesis.
In conclusion, we need to remember that mathematical descriptions are as useful as their accuracy permits, but they do not imply that reality is bounded within their formulae. As we can''t even reconcile General Relativity with quantum mechanics, it is clear we've a long way to go before we more fully understand the universe in which we briefly live.