Yes, just to emphasize this post -- I have read elsewhere that your declining these terms could lead to your account(s) being closed immediately. What makes anyone think they wouldn't do that?
Disagreeing with the terms could close your account, but this section is severable (can be disagreed with separately).
Generally, opt-out is added to reduce the risk that courts will throw out the arbitration clause as unconscionable (unfair). Companies know that most people won't opt out, and any class action brought by somebody who opts out will only apply to other customers who opted out- cutting damages by 99%+.
