Why should effective radiated power (ERP) be limited to a satellite that uses a linear transponder?
Why A linear transponder amplifies its whole passband at once, and the satellite's downlink transmitter has a fixed total power budget shared among every signal in that passband. Automatic gain control in the transponder sets the overall gain based on the strongest signal present, so one station running excessive ERP grabs a large share of the power and forces the gain down for everyone else. The result is that all other users' downlink signals get weaker. Good practice is to use only enough uplink power that your downlink is about as strong as the satellite's beacon, never stronger.
Watch out Telemetry corruption and out-of-band emissions are not what happens; the transponder stays linear and in band, it just redistributes its limited output power. Terrestrial interference is not the issue since you are pointing a beam skyward at a frequency the satellite is listening on.
Shared power pie: don't be louder than the beacon, or you eat everyone else's slice of downlink.