It will protect his own PC from future attacks because MCS will check every USB that is hooked up.
As for other computers, if you have installed AV/AM/FW and MCShield (in this case) then, other PC will be safe too. This is the best form of protection. I do not see where is the problem in that?
edit:
PS: MCS will also delete malware from USB mem-devices. USB will leave PC as clean and disinfected devices.