If you can't do your own research to give you the information you require I don't think you're in a position to intellectually debate with anyone. Your colleague is correct so it's pointless anyway.
I saw an excellent post earlier by ACautionaryTale which I hope she doesn't mind me copying here about what would happen in the unlikely event that Labour won the election:
Entrepreneurs relief scrapped and all capital gains to be be taxed at marginal rate (currently 20% after the allowance) - no incentive for small businesses to try to grow
Dividends to be taxed at marginal rate (which means after they've been taxed at 26% corporation tax they then get taxed again for the recipient meaning they actually get taxed at 66% or worse)
Corporation tax rising from 19% to 21% and 26% if turnover (note not profit) is over £300,000 - you could make a profit of £1000 and still pay 26% tax
Income tax rising to 50% if you happen to earn over £80K - which is only slightly above the MP's salary so they are ok
Married persons allowance scrapped - so a £250 tax rise for the poorest since to qualify you have to be a basic rate tax payer and the spouse has to be earning less than the personal allowance
200% second home tax even if accidentally inheriting or having to move and trying to sell
10% of uk based companies share capital to be "owned" by the government who will then pay some back to the workers - let watch all international companies remove their head quarters from the UK the day after election
Full employment rights from day one - so no chance to get rid early of people who don't perform - which is going to put companies off actually hiring people in the first place or just using temps.
Collective bargaining to be introduced across all sectors - removes the incentive to work harder for better pay or better negotiation
Maternity leave to be increased and flexible working to become a right - thats women having less chance of decent employment then as I for one would not hire one
Government policy to eradicate gender pay gap - the reason for it is because women IN GENERAL tend not to do the higher paid jobs because they don't like the hours, stress, committment or travel and are more family orientated. Women get paid the same for doing the same jobs.
Keeping sunday restrictions on trading - so we're still stuck in the 19th century
Ending two child cap - so basically reverting to paying people to have children whether they can afford it or not
Finding the magic money tree for WASPI women who if they read the news should have known about the pension changes - not anyone's fault if they didnt educate themselves
Rent controls and open ended contracts for renters - so how do you manage to evict the problem tenant? Pushes the balance too far into the hands of the renter and will actually reduce the supply of reasonably affordable rentals.
A Labour government will repeal the Fixed-term Parliaments Act 2011, which has stifled democracy and propped up weak governments. - this is hypocritical when they relied on it to STOP a general election for several months
Brexit - another year of uncertainty before we even start on trade deals.
Read that and inwardly digest and then have an intellectual debate with yourself as to why anyone would vote Labour.