Official Q&A: VRC 2019-2020: Tower Takeover

can a robot intentionally ram the towers in order to attempt to de-score cubes?

There are no rules explicitly preventing this, thus it is legal. Teams who choose to attempt this strategy should be mindful of the following rules:

<S1> If at any time the Robot operation or Team actions are deemed unsafe or have damaged the Field Elements or Cubes, the offending Team may be Disabled and/or Disqualified at the discretion of the referees. The Robot will require re-inspection before it may again take the field.

At a minimum, contact with the force required to dislodge a Cube may result in a warning, depending on the amount of damage incurred to the Tower as determined by the Head Referee.

<G16> Don’t clamp your Robot to the field. Robots may not intentionally grasp, grapple or attach to any Field Elements. Strategies with mechanisms that react against multiple sides of a Field Element in an effort to latch or clamp onto said Field Element are prohibited. The intent of this rule is to prevent Teams from both unintentionally damaging the field and/or from anchoring themselves to the field.

Using a mechanism to "bend" a Tower with the intent to dislodge a Cube would very likely be considered "latching" or "clamping" to a Field Element, depending on the specifics of the interaction.

<SG7> Use Cubes to play the game. Cubes may not be used to accomplish actions that would be otherwise illegal if they were attempted by Robot mechanisms. Examples include (but are not limited to): • Encroaching upon an opponent’s Protected Zone per <SG3>.

<SG3> Stay away from your opponent’s protected areas. Robots may not intentionally or accidentally, directly or indirectly, perform the following actions: [...]

Any Cubes that are Removed from Towers via this strategy would be subject to the constraints of SG3, via SG7.