First I want to get a quick correction out of the way, because you know how much I hate misinformation. CO2 Expeller claimed "It takes 15 years to get the energy out of solar cells that it took to create the solar cells in the first place."
This is a false statement. What his link showed is that it takes 10-15 years for solar PV to pay for itself. This has nothing to do with the energy it takes to create them, which is relatively minimal. On top of that, I believe these figures are out of date. At the business park where I work, they just installed solar panels as shading for a parking lot, and the park manager said the payback time is only 6 years. Solar PV prices have been dropping fairly dramatically recently - in fact there was Duke study concluding that they're now cheaper than new nuclear power.
http://www.ncwarn.org/wp-content/uploads/2010/07/NCW-SolarReport_final1.pdf
So back to the question at hand. I don't think anyone (other than some fossil fuel companies and those who are paid off by these companies) oppose the development of alternative fuel and energy technologies. The question is how much people are willing to fund their R&D and subsidize them. Some of the most politically conservative oppose all subsidies and think new technologies should be able to compete on their own in the free market.
The problem with this thinking is that new technologies are always expensive when first developed and produced, so it's very difficult for them to compete with long-established technologies which already have the benefit of the economies of scale. However when the new technology provides a public benefit in comparison to the established technology, as alternative fuels and energies do (cleaner air, water, domestic energy production, no concern about fuel supply, reduction in carbon emissions, etc.), there is justification to fund and subsidize these technologies to help them gain a foothold in the market and achieve a cost reduction via those economies of scale. In fact as discussed above in response to CO2 Expeller's comment, that's exactly what's happening with solar PV right now. Hybrids are another example - they were subsidized due to their public benefit (less oil consumption, less pollution, etc.), they gained a market foothold and their prices came down, and the subsidies were phased-out. Now they're competitive on their own.
However, you could call the opposition of any subsidies a valid reason to oppose development of alternative fuel and energy technologies. It just depends how much value you place on all those benefits alternative fuels and energies provide.
Opposition to specific alternative fuels can be valid too. For example, corn-based ethanol produces approximately the same net carbon emissions as burning gasoline, so at this point there's little justification to continue funding its development. However, the technology has paved the way for other more environmentally friendly sources of ethanol (i.e. switchgrass), so personally I think it was worth initially supporting and funding.
Some people have argued that wind turbines kill too many birds, but their avian death toll is dwarfed by utility transmission and distribution lines, collisions with motor vehicles, collisions with windows, pesticides, cats, etc. This is simply not a valid reason to oppose wind power.
http://www.awea.org/faq/sagrillo/swbirds.html
Others have claimed wind power is an 'eyesore', which is completely subjective (I strongly disagree), and thus also not a valid reason.
Another argument is that most sources of renewable energy can't provide baseload power. However, some can (geothermal and concentrated solar thermal, for example), and not being able to provide baseload does not invalidate their contribution to our power generation. Thus this is not a very valid reason for opposition either.
Ultimately the main reason for opposition is the cost and not wanting to fund subsidies. As I said, there is some validity to this opposition, as it simply depends how much you value clean air, clean water, domestic energy and job production, decreased reliance on fossil fuels, increased national security, reduction of global warming and ocean acidification, etc. etc. Considering all these benefits, personally I think alternative fuels and energies are well worth funding and subsidizing, but others disagree. But of course I'm right and they're wrong :-)
*edit @ Expeller* my criticism was not of your numbers, it was that you got the facts wrong. You used a monetary figure (15 years for ROI) and equated it with energy ("It takes 15 years to get the *energy* out of solar cells..."). I thought it went without saying that energy is not money, but apparently it needs saying twice.
As for the numbers, apparently you didn't notice that I did give a specific example. The ROI depends on how much energy you use. For a larger application like parking lot shading, more solar panels are used, and the ROI time decreases. For a smaller application like an individual residence, 10-15 years is probably an accurate ROI time. Even for a home it depends on how much energy is used. So we both made an error in making blanket statements about solar PV ROI time, when it depends on the size of the application. But regardless, you were still wrong to equate ROI time with energy.