Kurt's prior actions, arguably signifying that he views Finn's heterosexuality as a choice, were every bit as wrongheaded, if not more so. From Finn's point of view, he has been removed from his childhood home, forced to share a room with another person, a fellow student who has a crush on him no less, all while having to deal with the sudden fact that his mother has taken up with a new man. Kurt has been quite passive-aggressive, on one hand arranging to move in together with the jock who he has a crush on while lashing out at his father for bonding with said jock. Yes, Finn used a gay slur, but to be threatened with proverbial homelessness (IE - being thrown out of the house by Kurt's father) for losing your temper with your unwanted and sexually-obnoxious new roommate (be said roommate gay or straight) is a punishment that did not fit the crime, especially given that Finn had been forcibly removed from his own house and forced to live with Kurt and his father. Finn was intolerant not of Kurt's sexuality, but of Kurt's behavior as a classmate, teammate, and occasional friend.
Morever, it is obvious that the righteous-indignation thrown at Finn by Kurt's father, Burt (Mike O'Malley) comes not just from his offense at his son being scolded in a bigoted fashion, but rather overcompensation stemming from his own guilt, both over his failure to truly accept his son and his ease with which he bonded with the more 'traditional' step-son that is Finn. That's all well and good, as the scene up to that point was rooted in prior character development and worked as a powerful moment. But, from a purely storytelling and character perspective, the show faltered by not acknowledging that Kurt bore some responsibility for instigating the whole affair.
Kurt did not seem to realize how put-upon Finn had been feeling about the new living arrangements. Kurt (from the evidence thus far in the show) doesn't seem to realize that everyone of all sexual orientations should be able to reject potential suitors without fear of reprisal. He also didn't realize that in those moments and the moments involving his crazy scheme (which involved trying to snag Finn as an unwilling roommate in order to breed eventual romantic interest) that he was in fact personifying every negative stereotype regarding young gay men.
Which, again, would have been just fine on its own. The characters of Glee have never been portrayed as saintly and drama often comes when characters we like partake in behavior we disagree with and/or make decisions we abhor. But the show faltered by making the whole blow-out appear to be completely Finn's fault. Finn, who had been portrayed as empathetic, tolerant, and understanding of everyone around him, was presented as just another closeted bigot who needed to 'man up' and admit his own foibles. Finn was the one who had to 'reach out' in order to make proverbial amends. Finn was the one who basically had to round up the Glee squad in order to save Kurt from a bullying in the school hallways.
But, by apparently letting Kurt off the hook for his own behavior, and by allowing Kurt's father to tear his new step-son to shreds without bothering to inquire as to what had occurred, the show failed as anything resembling a 'teachable moment' for gay representations in mainstream entertainment. It was great acting and compelling drama, but the lack of appropriate follow-through inadvertently taught some genuinely awful lessons for viewers of all ages and sexual orientations.