That's one way to look at it. Another is that Shark Tank is itself a business and they're taking a risk putting you on TV; if you don't generate interest, the show could get cancelled because of poor ratings. In effect, they are investing in you and the success of your product, and I don't see why it's unfair they receive a return on your potential subsequent success.
The last episode of Shark Tank had 6 million viewers . If we pick $1/thousand impressions as a reasonable advertising cost, you'd have to spend $600K for 6 million impressions. It's difficult to overstate how good this deal is. That's what you'd be looking at paying for a Google ad that is displayed for a few seconds while a user searches or reads a page (not even looking at your ad). On Shark Tank you're holding people's direct attention for 5-15min.
For you to start losing money, ABC would need to take > 600K out of your business. At 5% equity, that equates to $12 million in distributable net profits. Let's say the life-time of your business is 10 years - that's $1.2 million net profit distributed to shareholders/year. To redistribute $1.2 million/year you're looking at (one imagines) at least 4 times that in net profit before taxes, i.e. $4.8 million. If your net profit margin is an optimistic and very healthy 30% that's $16 million revenue/year.
To be generating $16m revenue/year makes you a pretty successful business and the chances are if you got to that point it's because you were on Shark Tank. Very few people grow a business to that size without spending substantially more than 600K on advertising and investment.
At that point, assuming you still own 65% of the business (you negotiated 30% away to Shark), you're pulling in 780K (65% of $1.2m) per year vs. ABC's 60K/year. And this is a bad deal?