Should a cheating man pay for the baby if his mistress gets pregnant?

If he is the biological father, he does have a legal obligation.  

If mom requests child support through legal means, a DNA test is likely.  If mom requests any type of welfare for the child (including Medicaid) the court will order one then too.

Nobody should have to have a court force them to provide for their kids.. male or female.  My ex is my ex for several reasons, but being a deadbeat dad isn't one of them.  He paid child support without a court forcing him.  The only reason we had a court order for it was from a divorce settlement.  He figured if he got hungry or needed shoes, the kids probably did too.

If its not his child its not his moral obligation. 

If his mistress was knocked up by someone else why should he pay to raise the other mans child.  If it is his then he is the legal father of the child and the child has the right in the USA to have his/her father help pay to raise them until they are an adult

One reason child support exists is to let either parent know with sex and making a baby comes responsibility of raising it, so don't go around taking sex and parenting children with a grain of salt.  And I agree - if you make the baby, you will help raise that baby financially if nothing else.  If he is the legal father, then yes he should pay.  

If she takes him to Court for child support that is a huge YES!   Most states feel if you make the baby then you should pay for the care and up keep of same!

Who says he has no legal obligation, he most certainly does, this is not the 18th century, it doesn't matter how many women he gets pregnant, he is responsible for all of his children.  Why wouldn't he be, do you presume that the state should take care of the child?  He is most definitely the legal father if the mother declares and puts his name on the birth certificate, where did you go to school anywat,

Any man who father's a child should be responsible and help pay for the babies upbringing!

Yes 100% of course you should ! 

What are you talking about?  Any father has a LEGAL obligation if he IS the father. It's called CHILD SUPPORT. And yes, he owes it and should pay it!!  It doesn't matter if he's on the birth certificate or not--if he is the biological father of that child, HE OWES. LEGALLY.

He does have legal obligations.   It can be proven the child is his. At the least the mother can sue him for child support. 

If the child is proven not to be his child, then no he has no obligation. 

In most states they have to provide child support, so they have a legal and a moral obligation.