Well i dont really think its fair that your parents are stereotyping snakes in a biblical way but anyways, i think they should maybe try to understand that they are living creatures also and should not be looked upon negatively.
As for the bible quotes...my bf found a few. For example,
Amos 9:3, " And though they hide themselves in the top of carmel, i will search and take them out thence; and though they behid from my site in the bottom of the sea thence; will i commend the serpent and he shall bite them." (this proves that God used snakes to his own advantage so how can they be satanic creatures?)
Mark 16:12, " They shall take up serpents and if they drink any deadly things it shall not hurt them, they shall lay hands on the sick and they shall recover." (To me.. i interpret this as a biblical way of saying snakes help society. If you look in todays research snakes help farmers for rodent control for their crops, and snake venom has help create anti-venom to save peoples lives and also they are looking at maybe venom curing a lot of diseases.)
So basically if God did not intend for the serpent to be on this earth for us humans to admire and appreciate, he never would have instructed Noah to collect a male and a female to put on the arc.
Hope it helps and hope it shows your parents a new perspective of snakes but also be prepared because the Bible also catogarizes satan as a snake because its the only animal on earth that can kill its prey like satan can kill someones soul. Keep in mind that its only a symbol though...its not a fact because humans symbolizes things all the time and the bible was written by a human. For example.. X-mas/Christs birth=Santa Clause, Christs ressurection/Easter=Easter Bunny! So symbols dont mean anything!
Snake Lady & Chondro Python