What about arguements that plants are sentient? They respond to stimulia and that is what sentient is about, possessing senses. Well plants do.
As I said very early on in this thread, I'm vegan because I've not been given a reason not to be, other than "it tastes good". On balance, I don't think that's enough of an upside to justify the downsides, which include but aren't limited to the increased environmental impact of an omnivorous diet in an industrialised context, and the scientific evidence showing the pain of animals killed for food.
The small "upside" that I get to enjoy the specific taste of chicken or pork isn't enough to balance out the downsides in my opinion. Eating a vegan diet is just as nutritious, just as tasty (qualitatively speaking, of course, but what I'm getting at ids that a vegan diet is in no way tasteless or bland and that, indeed, there are enough vegan analogues so as to make even the "taste" issue almost moot) and just as simple if you live in an industrialised society. I lose virtually nothing, and the world gains a lot.
I brought up the example of littering earlier on. Dropping my litter on the floor might be easier for me, but I don't do it because my personal comfort is outweighed by the empirical and social damage littering does. On applying a similar empirical test to my diet, I came to the conclusion that the "benefit" for me of eating meat was just as selfish as the "benefit" of dropping litter.
I don't judge meat-eaters nor condemn them for their diet. I'm not holier-than-thou or hardcore or militant about my veganism. I just ask people to honestly look at the evidence and to actually weigh up this balance for and against for themselves. Most people, and I was one, just don't think about why they're omnivorous - they just *are*, always have been since birth.
So, that out of the way, let's address your "Well, you have sex for enjoyment only" point. What are the downsides of my sexual activity? If I were to cheat on my girlfriend, she's be sad, so I don't do it, no matter how "enjoyable" this might be. There are also STDs of course, but I'm tested as clean and monogamous, steps taken to minimise harm whilst retaining maximum enjoyment. I've thought about my sexual behaviour and its impacts on others, and taken steps to mitigate my behaviour back from unbridled hedonism based on a considered assessment of the impact of various courses of action which might be available to me.
Veganism's the same - no doubt, the harvesting of crops kills small field mice, for example, but I've taken steps to reduce "harm" as much as I can. I've thought through how various actions, or diets, open to me affect others, and mitigate my behaviour back from unbridled hedonism accordingly. It's all about thinking what you're doing, and doing that calculation of personal vs. global benefit... We all do this for many, many aspects of our lives - I can think of other examples including speeding, drug taking, social politeness, table manners - but its just that on the question of diet, many people don't.
On the sentience of plants - is your position that I should eat meat because plants are "sentient"? Because plants move towards the sun, I should give up on veganism and start consuming animal products again.