Well, not

>If you didn't agree with the purchase of Windows in 1998, you could have 
chosen not to buy it... by choosing not to buy a computer at all.

Not really, you can always build a computer from parts so no Windows installed.

The only 'moral issue' I can see if the 'network effect' of the proprietary exchange formats
used by proprietary software, this is an important one but it's not 'proprietary SW' per se:
one such SW which would transfer its data in an open format would be perfectly okay for me (if
it doesn't try to cripple the open input/output like Microsoft did for example).