I would not say that it is an attack on gay people, but it certainly plays on stereotypes about gay people and it plays on homophobic attitudes in society.
What makes this ad "funny" (if you think it is) is the idea that it would be mortifying and humiliating for it to even appear that a straight man was sexually interested in gay men. That is why the man with the hedge clippers is so taken aback when he notices the two men who are near to the Doritos. This plays on the idea that gay men are in some way repulsive and threatening to the masculinity of straight men.
So, this is not a direct attack, but it does use stereotypes and attitudes that are hurtful to many gay people.
I don't think it is an attack on Gay men because there was never any real discrimination against them made. The ad shows the two gay guys had suspected their neighbour as interested. The ad never identified whether the guy was lusting over the gay men or the chips. The reaction of the wife is understandable and anybody seeing a love one lust over something would have a reaction. I think it just an ad that brought in another sexual orientation that is not often used in advertisments today.