One cannot challenge a person's Catholicity by pointing out sins of the past. We are all sinners.
In addition to the little matter of abortion, about which one must be clear: Biden disavowed the Hyde Amendment, thus endorsing taxpayer-funded abortion up to and including the moment of live birth (and beyond, to be candid), Biden has a few other moral troubles.
The Catholic Church is crystal-clear on its views about MARRIAGE. There is only one type of marriage: man and woman. Period. The Church is crystal clear on its views about homosexual sodomy. It is abhorrent and sinful. Endorsing gay "marriage" is tacitly endorsing a relationship that is, by definition, characterized by a life of homosexual sodomy.
And while neither the Bible nor the Church have spoken definitively about the issue of adoption, there can be NO DOUBT that the Church abhors homosexual adoption, which Biden considers fine and dandy. Indeed, he supports the ACLU, which seeks to de-fund and attack the Church's adoption agencies, which decline to place adoptees with homosexual couples.
I'm not sure how Biden stands with the Archbishop of Washington, but the Bishop of Scranton has decreed that he is not to be dispensed Communion because due the aforementioned matters, he is not a Catholic in good standing.
I don't really give a shit one way or another whether he is a Catholic in good standing, but I do take offense at his attempt to secure the votes of other Catholics by representing himself as a "practicing Catholic," which status he manifestly lacks.