Environmental impact of food production of tomatoes would depend on the method of production and the season. Growing tomatoes in the winter in non-insulated greenhouses heated by coal energy would be very bad, obviously. Importing tomatoes by ship could be better in that case (CO2 tranport budget is usually under 10%), obviously seasonal produce is best.
Meat is not CO2 only, though. Other impacts of animal agriculture:
- Greenhouse gas emissions
- Deforestation (50% of pastures used to be forests)
- Land degradation
- Water pollution
- Water overconsumption
- Loss of biodiversity
- Antibiotic resistance
- Ocean dead zones
- Inefficient land and resource use
- Ethical concerns
- Contribution to zoonotic diseases
- Air pollution
- Eutrophication
- Soil erosion
- High energy consumption
- Chemical runoff from pesticides and fertilizers
- Destruction of habitats and ecosystems
- Inequality in global food distribution
- Public health risks from foodborne illnesses
- Nutrient pollution
- Strain on waste management systems
- Overfishing (40-70% of plankton gone, sharks 90% gone, fish almost gone in 2040's)
A whole lot more people don't eat meat than you realize. Some of us don't go around advertising that fact because we're tired of being ridiculed, but we still show up in surveys. I don't think some 5-10% of people on the street are "running up to people they don't know to announce shit like this".