(Comments copyright original authors)
There is no other way to protect unpopular views. The whole purpose of tenure is to allow scientists with new or minority ideas that are outside of the scientific/political/economic orthodoxy to continue to do research in spite of the fact that their work can't get wide publication. We make them prove that they are competent by meeting the extremely high standards of the tenure review process - getting tenure is no cake walk - then we give them the freedom to follow research avenues without regard to how popular that area of research is, and without fear that unconventional avenues or conclusions will cost them their job.
Part of the price we pay for this is that some people will be lazy. Academia as a whole feels that this is worth the risk because:
1. The tenure review process will screen out the overwhelming majority of the lazy people - you simply can't get tenure if you're lazy - it's too damn hard.
2. Carrying a few lazy professors is more than worth the benefit of having a faculty that is unafraid to voice the truth as they see it without fear of reprisal from administration, established researchers in their field, powerful alumni, government, etc.
3. Knowing what work will lead to something "useful" is tantamount to being able to predict the future. The idea that one can tell in advance where important breakthroughs will come from or where they will lead is a bean counter's fantasy. Therefore we have to trust that extremely competent scientists when allowed to follow their own chosen research paths without coercion will come up with important results. It's worked for us so far.
The argument I hear implicit in your words, that professors should be compensated for their research activities, is one I support. However, as I mentioned below, this is often not feasible because the "worth" of one's research is not always immediately apparent. Additionally, you are referring to tenured academics as lazy, which I simply cannot countenance. You glorify something that you do not understand. Therefore, though I am only a Ph. D. student at the moment, I wish to share my view (doubtless with its misconceptions) of the career as an aspiring academic:
Becoming a professor is not a career decision to be taken lightly and it is not for the lazy; it truly is something that must be born of a devotion to the pursuit of knowledge to the exclusion of almost everything else. The training process required to get a Ph. D. is lengthy, difficult, and generally unrewarding. True, we are generally funded while graduate students, but the funding is paltry, requires a TA or RA position at the institution unless you are fortunate enough to obtain a fellowship, and carries an expectation to devote every moment of our time to our studies and research. Even fellowships contain clauses prohibiting us from working without permission of the dean. Following a successful defense, most professors must undergo a more difficult and only slightly more rewarding postdoctoral position. These do not necessarily lead to tenure-track positions; approximately 10% will be offered assistant professorships, which carry an average salary of $44,939. In other words, after I complete my Ph. D. and a postdoc, I can look forward to starting at about $10,000 less per year than I would with most jobs I could attain right now with only a bachelor's degree in CS if I happen to be in this fortunate 10%. This is despite all of the work I have published without demanding anything in return (indeed, such work is expected). If I please my superiors and bring lots of grant money in for my institution (which involves writing a lot of proposals I'd rather not be bothered with, as they interfere with my research and other duties), I may eventually be granted tenure and perhaps rise in academic rank.
We are not compensated for publishing our research, so unless we choose to patent our innovations, our salary is our sole source of income.
A lazy person would not get this far. Anyone capable of enduring that much to reach this point is dedicated enough to the pursuit of knowledge to continue of his own accord because it is truly what he wishes to do.