2) The second, and probably more important point, is that Catholicism does not solely rest on the bible, unlike many forms of Protestantism. Thus, the idea that they pick and choose what's important in the bible is irrelevant as a criticism, because Catholics do not have the same premise as many Protestants - that is, only the bible is acceptable as a justification for Christianity.
Of course it's a valid criticism. As long as they're using 'because the bible says so' as an argument for or against anything, then the fact that they arbitrarily pick and choose when it is allowable to use 'because the bible says so' is a valid criticism. It only becomes irrelevant when they no longer give rules or arguments more weight just because they are presented in the bible, or when they give every rule & argument presented in the bible more weight. Criticising any religion for the way it uses the bible in support of its arguments is independent of any other arguments it might use.