Your logic, or lack thereof, defies me.
Yes, aluminum bends. So according to you all currently sold smartphones are defective and need to be recalled. The iPhone 5 and 5s should have been recalled. the original iPhone should have been recalled. Aluminum is lighter than steel and far less expensive than titanium. All phone manufacturers could make their phones with Titanium to avoid (avoid, it will still bend but at higher pressures) bending if you would be willing to pay about $2,000 for a smartphone.
Nobody has claimed that any aluminum smartphone can bend with the right amount of pressure. No manufacturer is claiming it cannot be bent.
In your case you should be looking at how did that much pressure get applied to your phone to slightly bend it while it was in an Otterbox. This would be a good question for the manufacturer of your case although it is possible you bent it placing it in the case.
All any of use have said here is it requires a certain amount of pressure to bend the phone. For 99.9% of users they haven't placed that much pressure on it.