What is with admins who will only use Cisco for everything regardless of cost?

I'm relatively new to the industry with only 4 years experience, but I've noticed more and more lately that some admins who have been doing this stuff for 10-15 years will only use cisco hardware. I'm not talking about big pieces of equipment, either.

For example I was talking about getting SFP's for my home lab and a few guys went on an unsolicited rant about how if I get SFP's from anywhere that isn't Cisco that I'm gonna "fry my home lab" or "expose my network". That seems a little extreme to me. This isn't the only example I can think of either. As long as stuff comes from a reputable vendor and is compatible does it really matter that much?