Nobody's denying the "authenticity" of the song. It's that it betrays a basic lack of understanding of the US and its problems.

Like, he complains about high taxes. If he's actually talking about working class / poor people, their taxes really aren't very high. The US does have a progressive tax system and people near the bottom aren't taxed that much. On the other hand, unlike most countries, the US also doesn't have a good safety net to help the least fortunate out. Because of that, taxes might feel like an awful burden when you're poor because you aren't getting the benefits... and then he goes on to complain about welfare... the very benefits that poor people should demand.

He (himself fat, if not obese) complains about obesity, and links it to welfare (also taking pot-shots at short people for some reason). It's not like people on welfare are eating so incredibly well that they become obese. It's that when you're poor, the system in the US makes it hard to eat nutritious food. First of all, processed food is relatively cheap, and it doesn't go bad, so it's a smart thing to buy if you're on a budget and catch it on sale. If you buy fruit and vegetables, they might go bad before you can use them. Many poor people also live in food deserts, so getting to the store to buy fresh food is very hard. If you're only working a 9-5 job and have a reasonable commute, and can easily get to a grocery store, you can afford the time to do meal planning and cook for yourself. If you're doing unpredictable shift work, and have to get around using unpredictable and slow public transit, and getting to a grocery store is an hour-long detour, it's hard to avoid unhealthy food because you can't count on being home to cook regular meals. Finding inexpensive but healthy food out in public is very hard.

On the subject of welfare / food stamps and obesity, I read recently that people having their food stamp / SNAP funds stolen is very common because SNAP only uses a basic swipe card that's easy to steal. Stealing people's SNAP money is rarely investigated, and they don't get their money back. For that reason, a lot of people on SNAP go to the store and spend all their SNAP money the moment they get it. If it's all spent, it can't be stolen. But, what can you buy that's going to last you a month until your next payment? It isn't fruits and veggies, it's canned foods, processed foods, high-sugar foods, etc.

So, yeah, he's "authentic", but he's also misinformed about the world. He's blaming welfare / welfare recipients as much as he's blaming the "rich men north of Richmond", when problem B is much, much more of an issue than problem A.