I don't agree with all the Tom-bashing on this thread.

True, Tom says that Vito has to give Sollozzo a day next week. But that proves nothing more than that Sollozzo has been previously discussed. To suggest that Tom has indicated to Sollozzo that the Corleones may be interested is a stretch. If nothing else, that would be very out of character for Tom.

There's no reason to believe that Tom has the ability or inclination to force Vito into a meeting he does not want to have. And the meeting wasn't the problem - the refusal was. Had Tom counseled Vito not to meet, things would likely have proceeed the same way. The only difference is that Sonny opened his pie-hole in the meeting, which you can hardly blame on Tom.

If memory serves, in a deleted scene Vito instructs Tom to add to his notes that Sollozzo has a background in prostitution. This shows that Vito is very familiar with Sollozzo outside of what Tom has told him.

Tom's counsel was ultimately irrelevant in the ensuing events. I don't see how Genco would have been able to forestall the impact of narcotics on the Corleones or the Cosa Nostra in general.