"the cons are that they do not need the legal support marriage gives. "
Regardless, it's true that both types of marriages can be supported with the same cause.
"My opponent conceded that incestuous and gay marriage do not need to give birth or take care of children"
What do you mean "conceded"?
I'm the one that gave you the solution to your problem with offspring. You started off your position with incestuous married folks that have children and I indicated not necessarily due to contraception, etc.
"As such, they have less needs than usual marriages. My opponent must overcome the fact that normal marriage have a huge burden on them, with assumption that they have more offspring to take care of, as most people marry in order to have sex without worry (as it can end up with having children). "
Why are you determining need? Your position for doing so is none. We don't have a part in people's marriages. Their reason is their business for marriage and theirs as far as a decision on children. Their purpose for marriage is between them.
"As such, because they carry on the idea of society, they deserve tax deductions, better rates on home and auto insurance, so on and so forth. My opponent vouches for equality, but civil unions already give the legal protection they need to live on without worry. Why do they deserve the same amount of massive benefits? "
Who knows? We know we can support both types of marriages on the same cause. Doesn't matter what the cause is for this debate.
"A homosexual relationship, regardless of how enduring it is as a bond of loving commitment, does not and cannot include sexual intercourse leading to pregnancy. Thus it is not marriage."
Legally it's a marriage. That's not debatable.
"Most people support civil union for homosexuals, in contrast to gay marriage."
Enough support is available to legislate same sex marriage. People support same sex marriage and whether realizing it or not, that support is applicable to incestuous marriage as there would be no contradiction based on the cause.
"Because of established traditions, because of expectations of married couples, civil unions would still be fair and just as they allow gays to establish a legal and formal bond. Because of its more general purpose, more people support it, allowing for greater happiness among the people. My opponent has not pointed out any problems with civil unions over marriages."
Why would I? Is the debate about same sex couples in civil unions versus being married?
Hello, is this thing on?
So again, the epicenter, if we can't support SAME SEX MARRIAGE AND INCESTUOUS MARRIAGE with the same cause, why not? What are the cons that are strong enough to defeat the possibility or purpose in doing so?