I feel your pain, it's an unfortunate situation and I'm sorry you have to deal with this issue.
We opened a complain with Symantec because their product blacklisted the whole domain dream.io, which hosts DreamCompute and DreamObjects. A blacklist so huge that it could affect dozen of thousands of perfectly safe websites and applications. We explained Symantec what dream.io domain does and why they should not blacklist it. They have lifted the block:
We found a virtual machine on DreamCompute that was hosting a phishing site. The reverse dns for that machine showed .dream.io as its domain and Symantec somehow decided it was a good idea to block everything in that area. We shut down that machine and notified the customer.
Symantec could have handled it better by contacting us to notify that dream.io was serving bad content: we receive similar notifications often from other vendors and partners. DreamHost has a security team whose job is also to deal with bad customers (or customers whose systems get compromised). Hopefully this incident will clarify in Symantec's records that dream.io should not be blocked.
You may want to tell them that your content is perfectly safe and that Symantec has added your hosting provider to the blocked list by mistake.
Also tell them they should complain with Symantec, too because blacklists have the side-effect of blanket censorship on perfectly safe content.