i agree with the OP and KMG. i can see both perspective.
if u cannot hold a snake, it's not necessarily a red flag for unhealthy animal. they gave u their reasons. anyway what is the store's reputation. as a breeder, retailer or whatever, your name and rep means a lot in the community. do they have a good track record? is their store clean, cages clean, general customer service good? and as pointed out, what is their health guarantee? or for reasons will they let u return an animal? the answer to these questions can help u a lot. or if u don't like the answers, just walk.