There are many factions within the world of open source, these include the Free Software and the Open Source pundits, the GPL and the BSD supporters, the libertarians and the communists.
These factions all have different reasons for the things they do and the things they don't; for some it is a matter of what is a right and what is practical, for others it is being altruistic to all people and for others it is getting the most out of a situation.
Briefly we shall sum up these groups:
The Free Software Foundation/GNU movement is a socio-political group for whom non-Free software is a social problem and Free Software is the solution.
The Open Source Inititive is a development methodology, to them non-Open Source software is a sub-par solution.
The BSDers (gotta get a better title than that) are a volunteer altruist group who give their work away for everyone. So everyone can get better. To them non-BSD code is irrelevant, it can be used and can be learnt from, but does not involved them.
The GPLers (still going to need another name) are volunteers who seek to recieve reimbursement for their contributions. Getting back what others make of their work. To them non-GPL code is code which will die, that without the GPL license to protect the code it will not be able to maintain its competitive edge against proprietary software.
Outside of these groups, most people view them singularly as either open source or free software, but within there is a fair bit of bitterness and conflict, because of the different reasons for their actions. They all hold different views on how things should be done. This creates an image of a discordant open source community, when, in fact, it is actually many smaller communities which have only loose ties to one another.