Why does Drummle almost come to blows with Startop at Jagger's house? Why do you think Jaggers says that he likes Drummle nevertheless?

Drummle almost comes to blows with Startop when he attempts to lighten the atmosphere and promote peace among Jagger's guests.

Hereupon Startop took him in hand, though with a much better grace than I had shown, and exhorted him to be a little more agreeable. Startop, being a lively bright young fellow, and Drummle being the exact opposite, the latter was always disposed to resent him as a direct personal affront. He now retorted in a coarse lumpish way, and Startop tried to turn the discussion aside with some small pleasantry that made us all laugh. Resenting this little success more than anything, Drummle, without any threat or warning, pulled his hands out of his pockets, dropped his round shoulders, swore, took up a large glass, and would have flung it at his adversary's head, but for our entertainer's dexterously seizing it at the instant when it was raised for that purpose.

In my opinion, Jagger puts up with his behavior because he has something planned for Drummle at a later date.