I agree that more diversity in the software ecosystem will cause critical bugs to have less impact to the world overall, and will hopefully drive competition to make the offerings more efficient and stable. However I think that this is a straw-man and the real conclusion we should draw is this:
When you write code, you are going to screw up. If you aren't writing bugs that people notice, you aren't working on anything worthwhile. While the bugs that were found were costly and dangerous, the question is were these found quicker than a closed source solution? Were they fixed faster than a closed source solution? Is there anything that can be done to allow quicker roll back or disabling of vulnerable features? When you write code, you need to design for failure, because it will happen and plan so that the recovery will be as quick as possible.
Adding additional software library offerings will only add stability in the sense that one particular vector wont affect as much of the Internet, but you introduce more surface area for attackers to poke at, and more vulnerabilities overall. Given the challenges to write really solid code, I think I'd like to have fewer, but really well vetted open source software solutions. Of course, I am not correct in this opinion, as there are no 'right' decisions here.