FYI, Magpul did respond on the you tube video comments section. They did test stronger buttons, but determined it was better to use the plastic one as a sacrificial part. I can't blame them as a steel one would probably damage more expensive parts. It's a pretty good response on the video. Kudos to them for posting it.
Oh, and they said they will replace the part for us. Obviously disassembly/reassembly isn't an issue for us, nor would it be for anyone who brought it to us for repair.