Actually, you asked for opinions, which is what you can expect to find here, or on any forum. If you want to make your decision based purely upon studies, then go read what you can find, evaluate accuracy and applicability, and make your decision. You appear to have done that, but are now looking for contrary opinions, probably because you have doubts about the decision you made. If that's not the case, then you were trolling for exactly the type of responses you received. In either event, you got what you asked for. You shouldn't have asked for it, in the manner you did (which was very "challenging"), if you were going to respond in such a thin-skinned manner.

Also, you are making your decision based not on the factual evidence you claim to seek and use as a scientist, but using your own anecdotal analysis of what body part is going to be injured, and how biking is inherently safer than riding a horse. Based on what, exactly? Yet at the same time you admit to being a total newb as a rider that can't ride a straight line. Yep, that sure sounds safer! Have you stopped to think that, just maybe, those folks who have been riding awhile, and actually experienced accidents on a bike, might just know a teensy weensy bit more about how likely it is to hit your head, and what that can mean. You know what it's like on a horse, and wear a helmet as a result of that knowledge. We know what it's like on a bike, and wear a helmet (or not) as a result of that knowledge.

Nobody here is saying you have to do what they do, and nobody is far away in tone from what you have posted. Either go back to your studies and hush up, or listen (objectively) to the responses you provoked.