[quote name='daroga']Yeah? By "reason" and "logic" I assume you mean "arbitrary personal guidelines."[/QUOTE]
It's very easy to look at both sides of argument and then use basic reasoning and logic in order to determine which evidence has more weight, which arguments are more sound, and therefore which course of action is the most reasonable. Your argument used a slippery slope, which is a logical fallacy, and therefore not valid.
[quote name='daroga']What's the difference between first cousins or a brother and a sister that want to get married, or have a civil union, or whatever, and two homosexuals? *snip*[/QUOTE]
Again, you're using the slippery slope technique, but I'll go ahead and answer it anyway.
The most obvious problem with your argument is the point at which you've decided to start your slope. You've decided that a union between two people doesn't start on the slope to badsville until it becomes something other than a heterosexual male and female. This is, of course, is a completely arbitrary choice and makes the argument pretty much worthless. You could make an argument for tradition, but that's a logical fallacy.
You're also putting homosexuality in the same class as incest, which it isn't. The former is a generalized notion of the type of person someone is attracted to, while incest is an act that is perpetuated between individuals. You could make the argument with incest that the two people, assuming they're both consenting, would likely fit in each other's generalized attraction group, but even then you're talking about individuals inside a much larger group, not a group in of itself.
Franky, I think any two adults should be able to have sex provided both are in the mental, physical, and emotional state to consent to the act. Oftentimes in incestuous relationships, however, the ability of one of the participants to consent is in serious question, even when that person is an adult, and because of the close familial relationship, trying to classify the acts as "rape" under the law could make the law too broad or could prove a fruitless endeavor that does not cover enough situations in order to make the law effective. Hence, you have laws against incest, which, while they can be applied against two related people in a completely consensual sexual relationship, are actually meant to protect victims of sexual abuse within a family and can be especially effective when the victim is an adult, as many of the laws protecting children would not apply.
So that kinda covers the "Homosexualiy====>Incest" slope, but we're now left with the marriage question, which is really just a question of government regulation. Here's where things get a little wobbly. It would be nearly impossible to create some form of legal, state-recognized marriage that would cover everyone. The number of cultures and religions in our country prevents that. So, in reality, the best solution would to simply have no state-sponsored marriage at all. That allows everyone of consenting legal age to draw up their own marriage contracts with their own terms or to simply leave it as a nice ceremony that they have, whichever they feel is best for them. You're then left with the problem of insurance, next of kin rights, etc., but those issues would likely be resolved by simply filling out a form that says "This is my spouse:_______" whenever the question needs to be resolved. You can also get into the question of what government should and not be doing, if you wanted.
[quote name='daroga']Homosexuality is offensive to me morally[/QUOTE]
It shouldn't be. If I may somewhat borrow your slippery slope technique for a moment; there is nothing morally wrong with two heterosexual people having consensual sex, so therefore there should be nothing wrong with two homosexual people having consensual sex. There really is no difference between the two acts. The only real argument one could fathom that would define one as morally superior as the other would have to come from religion, and using fairy tales is not a legitimate argumentative practice.
[quote name='billyrox']what do you base reason or logic on? just something you "intuitivly know"? or is it something that is completely relative? isn't this just a construct that our current society deems allowable? afterall, men having sex with men was something completely frowned upon in many cultures for thousands of years, but now it seems norm in our culture. [/QUOTE]
This is a variation on the "You can't judge something by your culture" or "It's good for their culture, so we can't judge." arguments that you often get from jackass anthropologists who can't wrap their heads around the fact that things really can be reasoned out to be "bad" or "good". These arguments of course lead to only one conlusion; there really is no such thing as right and wrong and that making judgements on people's behavior or its impact is completely subjective. This isn't true at all, though.