The main reason that abiogenesis is contrary to observation is that life has only been observed to come from life. It has never been observed to come into existence from dead matter spontaneously. The simple fact is that the line between life and non-life spontaneously only goes one way, that is a living thing dies such that life becomes non-life. We do not see corpses spontaneously come back to life such that anyone seeing a dead person come back to life would rationally conclude that it was an act of God. Not only are there no examples of abiogenesis being observed, but everything we observe says it cannot happen.
While this is possible within science there are legitimate reasons for not being able to observe a phenomenon directly, the simple fact is that abiogenesis is directly contrary to what we do observe. We observe living things dying but we never observe dead things coming to life. We observe living things producing other living things; we never observe living things coming from non-living matter. Consequently, this naturalistic idea for the origin of life is completely contrary to observation and therefore it is unscientific.
