There are gentler ways to win an argument than bullying ("I don't believe you have much experience dealing with corporations, and possibly even clients in general"). Such as with valid arguments that have weight. Which I don't see in your reply.
First of all, I'm working on IT projects that are probably way out of your league. The fact that I don't have time to make websites for small business and private parties doesn't mean that I wouldn't know what I'm talking about. The other night I solved a layout problem on Stack Overflow that nobody else knew how to solve. A question that was posted by one of the SO moderators, and that got a bunch of up-votes and favorite-question stars in no-time.
Also, simple logical reasoning disproves your basic point, even if I would be a novice. Nowadays, there are only two kinds of users who still have IE6/7. The first kind is the people who still have a Windows 95 computer. I don't think any webdev in their right mind would wanna code for them. The second kind is the employees of large companies with XP computers, obliged to use it for their intranet sites. Not much wrong with that, but they won't use that same IE6/7 for the internet sites they visit. Simply because they've learned that those sites are not functional anymore with such an old browser. They will get alerts all the time, and will use FF or Chrome, which they have will have installed on their computer as well.
Those large companies have their own IT staff, making their own intranet websites. I don't think many PHP Freaks webdev-visitors will be asked by such companies to make a site for them. In fact, I would think the number is zero. Apart from you, maybe.
Furthermore, the (American) stats on http://gs.statcounter.com/#browser_version-US-monthly-201305-201405 show that even IE7 has left the building. And which corporations are you referring to that have sites that need IE6/7 to be functional and esthetically appealing? Unless you have a time machine, I don't think there are such corporations anymore. N=0, again.
Nonetheless, I wanna make friends with you. How about if I write a tutorial for PHP Freaks, explaining the basics of modern Ajax, including the pitfalls regarding the implementation of the responseText, which there still are a number of? I'll do it for free.
Just think about it. But even if you reject this offer, you still have to delete this whole thread. Because what you are stating in your original post translates to "If you don't use layout tables, don't come asking here for advice" on the CSS section of PHP Freaks. Time to upgrade, Josh.