The easiest way is to make whatever criticism you're going to make (they probably steal wages more than big companies, they're nepotism factories, a lot of them just aren't run competently, etc.) with language that's less abrasive than "fuck small businesses." Give specific examples and do it in the way you'd criticize some band you aren't really into. Sometimes you can get away with a surprising amount if you state it matter-of-factly.

Another tactic is to use a story or an anecdote to reframe what people think of when they think of a small business owner. This is basically what CTH does with the "runs a ski-doo dealership and thinks they're a captain of industry" bit. Don't let people imagine some earnest, hardworking restauranteur who works 100 hours a week and is just trying to scrape by -- talk about some 45-year-old Trump diehard who pays undocumented workers under the table at his landscaping company, cheats on his taxes, and hits on the high school girl he hired to answer phones at the office. You still want to acknowledge the existence of both (at least in a longer conversation), but focus the conversation on the ones who are least sympathetic and who most embody easy criticisms.

I've also had some success with "'think of the small businesses' is used as a stalking horse for the interests of big businesses the same way 'think of the children' isn't actually used by people who deeply care about kids."