Stands to reason, that its better to get your vitamins and minerals in a natural state than man made. You make a good point regarding the acid effect of synthetic vitamins. Two things add to the problem. First is a persons level of absorbsion. If it is not good then vitamins are quickly passed through and do little or no good. Second, most people take way too many supplements. The old saying, " If one is good, then two must be better," does more harm, than good. Now the liver is over loaded trying to process all the unnatural junk.
We need supplements, but in the right form and just enough to supplement a good diet.