Likewise, if these are actually causing you issues, then complain with details. Many advertising sites have restrictions on what content can be displayed - the best example is that only static images are allowed on most roadside advertising screens aimed at drivers - there is no reason why suitable restrictions couldn't be placed on the content on the Euston screen if they are actually causing problems. These types of screens have been in use for decades, and there is mountains of research on both the positive and negative effects of the content shown this way.
If you (and the others making similar complaints), don't want the advertising at all, then that should be the base of your complaint - not wrapped up in vague "somebody might have an adverse effect" reasoning. Most of the complaints actually made on these threads are about things that can be altered or changed without removal of the advertising screen, but the solution that most posters have is removal is the only option.
It's very similar to the widely held belief on this site that all LED lighting is overly bright and harsh. It's a complete fallacy, with brightness, colour temperature, fixture type and directioness (is that a word) being choices made by operators and ROSCO's. If people want better lighting, they should be complaining that the quality of the light is too bright / too cold / shines directly in their eyes, rather than complaining that LEDs are being used.