That's not even one of the main arguments, besides no one is stopping them from loving each other. You can love someone without being married, cmon bro.

Gays and straights are entitled to the right of marrying the opposite sex, both are not entitled to marrying the same sex. Equal.

People don't have the liberty to do whatever they want that will make them happy. Murder, rape, etc.

Lol, marriages recognized by the government and literally everyone else doesn't concern anyone else? Cmon bro nothing is stopping them from forming relationships and loving each other, marriage is a different field which comes with federal recognition.

In response to the equal rights point: Everyone does have the same right to marry someone of the opposite sex. Straight and gay can marry the opposite sex alike, and both cannot marry the same sex, thus equal rights.

In response to general: The topic is more nuanced than, "should we let people love who they want". Nobody is stopping them from forming a relationship, however marriage is something that by definition is between male and female, it's in essence impossible for them to get married without being contradictory. There are many policies that change with marriage encompassing more than just a male and female relationship. And to do that is more work, deceiving, and futile considering there are civil unions for gay couples.