A maxim of communication theory says that conflicts are seldom about the topic discussed. Almost always, they are about the relationships between the people arguing.
For instance, World War I did not start because an archduke was assassinated, but because of the complicated grievances that had divided Europe into two arm camps were triggered by the assassination.
In the same way, the conflicts between Ubuntu and its commercial counterpart Canonical on the one hand and other free software projects on the other hand are not just about Unity, the wording of the Canonical Contributors' License Agreement, the technical differences between Mir and Wayland, or any of the half dozen other issues being so passionately discussed at any given time.
Contrary to what Ubuntu supporters sometimes claim, the conflict has little to do with jealousy. After all, Canonical has yet to turn a profit, and has had its share of failures, such as the Ubuntu Edge crowdfunding campaign.
Nor do you find the same level of animosity directed at free software companies that actually are successful.
True, the free software community has always been suspicious of commercial companies -- to the point that almost a third of those who answered a recent poll on FOSS Force thought, with no proof whatsoever, that Red Hat might have a backdoor in its code for the convenience of the American government.
However, the criticism of Red Hat is nowhere near as constant as what Ubuntu and Canonical receive.
I suspect that the community is less jealous of Ubuntu and Canonical than disappointed. From its earliest days, Ubuntu promised to transform free software, yet somehow that has never happened. Despite some advances in desktop usability -- especially in the first few years -- Ubuntu is nothing more than a distro among other distros.
It might be the most popular distro, but it has rarely managed to innovate more than rivals like Fedora that do not boast so regularly about their contributions. To this extent, Ubuntu is a victim of its own inflated promises, as well as its failure to deliver on them.
But even more to the point, Ubuntu has always been a maverick in the community. Again and again, at times through ignorance, and at times through haste and different priorities, Ubuntu has ignored the unwritten conventions of the community. All too consistently, it has failed to give due credit, to make decisions within the community and to observe the usual relationship between upstream and downstream projects.
Worst of all, from the traditional perspective, it has gone against these norms while claiming leadership of the community. Most likely, it could not have antagonized large sections of the free software community if it was deliberately trying.
The only return that free-licensed software promises is credit for your work. That promise remains important to many developers even today, when many are getting paid for their work.
However, Ubuntu has frequently been slow to give credit to other developers and projects. Neither the Ubuntu nor Canonical home pages mention Linux, although the Ubuntu page proclaims the distribution "the world's most popular free OS" in the title bar, and the Canonical page mentions "open source" twice.
Debian, the distribution that Ubuntu remains based upon, is similarly unmentioned at the top levels of the sites. When the Ubuntu wiki gets around to acknowledging Debian, it does so partly in language that reverses the relationship, declaring that "Every Debian developer is also an Ubuntu developer, because one way to contribute to Ubuntu is to contribute to Debian" -- as though Ubuntu was the parent distribution and Debian was the off-shoot.
To say the least, such behavior comes across as ungracious. Add the Canonical Contributors' License Agreement, which makes all contributions the property of Canonical, and reserves the right to make them proprietary, and the ungraciousness is only compounded. At least when a non-profit like the Free Software Foundation requests copyright assignment, you can be assured that your code will be used as you want it to be used.
Until about 2010, Mark Shuttleworth, Ubuntu's and Canonical's founder, could call himself Self-Appointed Benevolent Dictator for Life and pass it off as a joke. After all, other examples of centralized decision-making exist in free software, including Linus Torvald's control over the Linux kernel. So long as this control is tempered by an openness to input from the rest of the project, few object too strenuously.