I have a mechanistic and reductionist view of the universe; I don't believe we can really understand a thing until we understand all its components, all the way down to the sub-atomic particles (and Quantum Mechanics being what it is, you might get an arguement from me even then).
I have a prejudice against biology as a woefully gross and inexact science; this is not my high school biology teacher's fault (she did a terrific job) - it just seems that way to me.
Where Biology is concerned, the reductionist view means a better understanding of both physics and chemistry is required first. So far as I can see, only the field of Molecular Biology has these necessary underpinnings to the training.
When it is understood well enough to simulate biological processes accurately on a computer without resorting to tests on living subjects, I'll change my opinion. This is not about "animal rights"; it is about random trial and error versus prediction from accurate models.
That isn't to say that the pioneering work that many Biologists are doing isn't valuable - quite the contrary. They're collecting empirical data that will be precious. However, I believe that it is premature to draw any really big conclusions from those observations - if one keeps questioning the models with "why?", you'll quickly hit a point where the respondent will either say, "I don't know", or "It Just Is."