It's a shame, really, but in the modern age, who doesn't have a laptop at the very least??
Honestly speaking, I'm pretty sure most computers made in the last ten or so years can run Terraria. The required specs aren't very high, seeing as I can run 1.3 without any fps/lag issues on a Macbook Air. Despite the game not even having been released for Mac OSX yet.
Kinda weird how Macs tend to run games on higher fps than my PC. Is this why PC gamers don't like Mac?
What an ignorant thing to say. Not everyone has enough use for a laptop to make the expense worthwhile or simply cannot afford the luxury to begin with. Younger kids often simply use family computers instead of having their own, too, which can cause this sort of problem when they travel. Also, lots of poorer people do not have a single computer, much less a more expensive portable version. You'd, I'm sure, be astounded to know that many do not even have homes (yes, I'm talking about within 1st world countries). The privileges you enjoy are not universal, I'm afraid.
Your lag issues could be caused by the relevant specs of your Macbook being better than your PC (you give zero information in that regard), by poor compatibility of some hardware/software, by a bug (or many), or potentially your PC is simply poorly maintained (viruses, lacking driver upgrades, not defragged in ages, dying hardware, etc.). The reason is not, I promise you, because of super amazing Mac engineering.
PC gamers dislike Mac because the same specs cost, generally, a minimum of 2x as much for nothing more than the brand. Also, the hardware options for customization and improving the system are.. severely lacking (read: abysmal at best) as well. Macs have their uses (graphics/music production), but as general/gaming machines they are lacking (again, at comparable price points to other machines). Essentially though, I think the biggest thing people dislike about Mac are its users who seemingly have to bring up how "amazing" their systems are in everything, even forum threads that have absolutely nothing to do with Macs.