You have not been through the holy wedding ceremony, Martha was saying to her adopted son. You have squandered your right to be one of us. I cast you out. Do not touch the woman you hold in your arms. And be gone with you in the morning.
I don't think that's what happened at all with the phone call. It was just a matter of bad timing--Martha was worried when she couldn't reach Clark, thought he might've left without just one more goodbye (she was actually trying to keep him as long as she could on the planet,
not to "cast him out," as you said in your next paragraph), and wanted to make sure that he was still there for at least that one night. Who knew when she would see her only, and most-loved child again?
Martha wasn't trying to cast him out, or even to stop what Clark and Lois were doing (she didn't even
know what they were doing before she called, so how could she have an opinion about whether or not they should continue?).
The reason Lois & Clark stopped, I think, had more to do with the moment being ruined by the phone call itself than any imaginary aspersions that Martha might have cast on them.
In fact, I've always gotten the impression from the series that Martha would be perfectly okay with it if she knew that L&C had been having sex before they were married--she's just cool like that.
It was L&C themselves, after all, who decided to wait until they were married, and Martha who jokingly asked--mere
hours after she'd met Lois--if she and Clark were sleeping together, fully willing to give them both Clark's childhood bedroom while they stayed in Smallville during GGGoH.
