Child Support Owed When Child Is Not Mine

Since I don't know what I'm talking about, I thought I'd post the relevant statute for everyone's perusal... including Infinity, who seems to think he's the only one who can be right. However, he doesn't have a legal basis for what he speaks:

7646. (a) Notwithstanding any other provision of law, a judgment establishing paternity may be set aside or vacated upon a motion by the previously established mother of a child, the previously established father of a child, the child, or the legal representative of any of these persons if genetic testing indicates that the
previously established father of a child is not the biological father of the child. The motion shall be brought within one of the following time periods:
(1) Within a two-year period commencing with the date on which the previously established father knew or should have known of a judgment that established him as the father of the child or commencing with the date the previously established father knew or should have known of the existence of an action to adjudicate the issue of paternity, whichever is first, except as provided in
paragraph (2) or (3) of this subdivision.
(2) Within a two-year period commencing with the date of the child' s birth if paternity was established by a voluntary declaration of paternity. Nothing in this paragraph shall bar any rights under subdivision (c) of Section 7575.
(3) In the case of any previously established father who is the legal father as a result of a default judgment as of the effective date of this section, within a two-year period commencing with the enactment of this section.
(b) Subdivision (a) does not apply if the child is presumed to be a child of a marriage pursuant to Section 7540.